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The Info List - Deoxyribozyme


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Deoxyribozymes, also called DNA
DNA
enzymes, DNAzymes, or catalytic DNA, are DNA
DNA
oligonucleotides that are capable of performing a specific chemical reaction, often but not always catalytic. This is similar to the action of other biological enzymes, such as proteins or ribozymes (enzymes composed of RNA).[1] However, in contrast to the abundance of protein enzymes in biological systems and the discovery of biological ribozymes in the 1980s,[2][3] there are no known naturally occurring deoxyribozymes.[4] Deoxyribozymes should not be confused with DNA aptamers which are oligonucleotides that selectively bind a target ligand, but do not catalyze a subsequent chemical reaction. With the exception of ribozymes, nucleic acid molecules within cells primarily serve as storage of genetic information due to its ability to form complementary base pairs, which allows for high-fidelity copying and transfer of genetic information. In contrast, nucleic acid molecules are more limited in their catalytic ability, in comparison to protein enzymes, to just three types of interactions: hydrogen bonding, pi stacking, and metal-ion coordination. This is due to the limited number of functional groups of the nucleic acid monomers: while proteins are built from up to twenty different amino acids with various functional groups, nucleic acids are built from just four chemically similar nucleobases. In addition, DNA
DNA
lacks the 2'-hydroxyl group found in RNA
RNA
which limits the catalytic competency of deoxyribozymes even in comparison to ribozymes.[5] In addition to the inherent inferiority of DNA
DNA
catalytic activity, the apparent lack of naturally occurring deoxyribozymes may also be due to the primarily double-stranded conformation of DNA
DNA
in biological systems which would limit its physical flexibility and ability to form tertiary structures, and so would drastically limit the ability of double-stranded DNA
DNA
to act as a catalyst;[5] though there are a few known instances of biological single-stranded DNA
DNA
such as multicopy single-stranded DNA
DNA
(msDNA), certain viral genomes, and the replication fork formed during DNA
DNA
replication. Further structural differences between DNA
DNA
and RNA
RNA
may also play a role in the lack of biological deoxyribozymes, such as the additional methyl group of the DNA
DNA
base thymidine compared to the RNA
RNA
base uracil or the tendency of DNA
DNA
to adopt the B-form helix while RNA
RNA
tends to adopt the A-form helix.[1] However, it has also been shown that DNA
DNA
can form structures that RNA
RNA
cannot, which suggests that, though there are differences in structures that each can form, neither is inherently more or less catalytic due to their possible structural motifs.[1]

Contents

1 Types

1.1 Ribonucleases 1.2 RNA
RNA
ligases 1.3 Other reactions

2 Methods

2.1 in vitro selection 2.2 in vitro evolution

3 "True" catalysis? 4 Applications

4.1 Drug clinical trials 4.2 Sensors 4.3 Asymmetric synthesis 4.4 Other uses

5 See also 6 References 7 External links

Types[edit] Ribonucleases[edit]

The trans-form (two separate strands) of the 17E DNAzyme. Most ribonuclease DNAzymes have a similar form, consisting of a separate enzyme strand (blue/cyan) and substrate strand (black). Two arms of complementary bases flank the catalytic core (cyan) on the enzyme strand and the single ribonucleotide (red) on the substrate strand. The arrow shows the ribonucleotide cleavage site.

The most abundant class of deoxyribozymes are ribonucleases, which catalyze the cleavage of a ribonucleotide phosphodiester bond through a transesterification reaction, forming a 2'3'-cyclic phosphate terminus and a 5'-hydroxyl terminus.[5][6] Ribonuclease
Ribonuclease
deoxyribozymes typically undergo selection as long, single-stranded oligonucleotides which contain a single ribonucleotide base to act as the cleavage site. Once sequenced, this single-stranded "cis"-form of the deoxyribozyme can be converted to the two-stranded "trans"-form by separating the substrate domain (containing the ribonucleotide cleavage site) and the enzyme domain (containing the catalytic core) into separate strands which can hybridize through two flanking arms consisting of complementary base pairs. The first known deoxyribozyme was a ribonuclease, discovered in 1994 by Ronald Breaker while a postdoctoral fellow in the laboratory of Gerald Joyce
Gerald Joyce
at the Scripps Research Institute.[7] This deoxyribozyme, later named GR-5,[8] catalyzes the Pb2+-dependent cleavage of a single ribonucleotide phosphoester at a rate that is more than 100-fold compared to the uncatalyzed reaction.[7] Subsequently, additional RNA-cleaving deoxyribozymes that incorporate different metal cofactors were developed, including the Mg2+-dependent E2 deoxyribozyme[9] and the Ca2+-dependent Mg5 deoxyribozyme.[10] These first deoxyribozymes were unable to catalyze a full RNA
RNA
substrate strand, but by incorporating the full RNA
RNA
substrate strand into the selection process, deoxyribozymes which functioned with substrates consisting of either full RNA
RNA
or full DNA
DNA
with a single RNA
RNA
base were both able to be utilized.[11] The first of these more versatile deoxyribozymes, 8-17 and 10-23, are currently the most widely studied deoxyribozymes. In fact, many subsequently discovered deoxyribozymes were found to contain the same catalytic core motif as 8-17, including the previously discovered Mg5, suggesting that this motif represents the "simplest solution for the RNA
RNA
cleavage problem".[6][12] The 10-23 DNAzyme contains a 15-nucleotide catalytic core that is flanked by two substrate recognition domains. This DNAzyme cleaves complementary RNAs efficiently in a sequence specific manner between an unpaired purine and a paired pyrimidine. DNAzymes targeting AU or GU vs. GC or AC are more effective. Furthermore, the RNA
RNA
cleavage rates have been shown to increase after the introduction of intercalators or the substitution of deoxyguanine with deoxyinosine at the junction of the catalytic loop. Specifically, the addition of 2’-O-methyl modifications to the catalytic proved to significantly increase the cleavage rate both in vitro and in vivo. [13] Other notable deoxyribozyme ribonucleases are those that are highly selective for a certain cofactor. Among this group are the metal selective deoxyribozymes such as Pb2+-specific 17E,[14] UO22+-specific 39E,[15] and Na+-specific A43.[16] First crystal structure of a DNAzyme was reported in 2016.[17][18] RNA
RNA
ligases[edit] Of particular interest are DNA
DNA
ligases.[5] These molecules have demonstrated remarkable chemoselectivity in RNA
RNA
branching reactions. Although each repeating unit in a RNA
RNA
strand owns a free hydroxyl group, the DNA
DNA
ligase takes just one of them as a branching starting point. An accomplishment unattainable with traditional organic chemistry. Other reactions[edit] Many other deoxyribozymes have since been developed that catalyze DNA phosphorylation, DNA
DNA
adenylation, DNA
DNA
deglycosylation, porphyrin metalation, thymine dimer photoreversion[19] and DNA
DNA
cleavage. Methods[edit] Main article: Systematic evolution of ligands by exponential enrichment in vitro selection[edit] Because there are no known naturally occurring deoxyribozymes, most known deoxyribozyme sequences have been discovered through a high-throughput in vitro selection technique, similar to SELEX.[20][21] in vitro selection utilizes a "pool" of a large number of random DNA
DNA
sequences (typically 1014–1015 unique strands) that can be screened for a specific catalytic activity. The pool is synthesized through solid phase synthesis such that each strand has two constant regions (primer binding sites for PCR amplification) flanking a random region of a certain length, typically 25–50 bases long. Thus the total number of unique strands, called the sequence space, is 4N where N denotes the number of bases in the random region. Because 425 ≈ 1015, there is no practical reason to choose random regions of less than 25 bases in length, while going above this number of bases means that the total sequence space cannot be surveyed. However, since there are likely many potential candidates for a given catalytic reaction within the sequence space, random regions of 50 and even higher have successfully yielded catalytic deoxyribozymes.[21] The pool is first subjected to a selection step, during which the catalytic strands are separated from the non-catalytic strands. The exact separation method will depend on the reaction being catalyzed. As an example, the separation step for ribonucleotide cleavage often utilizes affinity chromatography, in which a biological tag attached to each DNA
DNA
strand is removed from any catalytically active strands via cleavage of a ribonucleotide base. This allows the catalytic strands to be separated by a column that specifically binds the tag, since the non-active strands will remain bound to the column while the active strands (which no longer possess the tag) flow through. A common set-up for this is a biotin tag with a streptavidin affinity column.[20][21] Gel electrophoresis based separation can also be used in which the change in molecular weight of strands upon the cleavage reaction is enough to cause a shift in the location of the reactive strands on the gel.[21] After the selection step, the reactive pool is amplified via polymerase chain reaction (PCR) to regenerate and amplify the reactive strands, and the process is repeated until a pool of sufficient reactivity is obtained. Multiple rounds of selection are required because some non-catalytic strands will inevitably make it through any single selection step. Usually 4–10 rounds are required for unambiguous catalytic activity,[6] though more rounds are often necessary for more stringent catalytic conditions. After a sufficient number of rounds, the final pool is sequenced and the individual strands are tested for their catalytic activity.[21] The dynamics of the pool can be described through mathematical modeling [22] , which shows how oligonucleotides undergo competitive binding with the targets and how the evolutionary outcome can be improved through fine tuning of parameters. Deoxyribozymes obtained through in vitro selection will be optimized for the conditions during the selection, such as salt concentration, pH, and the presence of cofactors. Because of this, catalytic activity only in the presence of specific cofactors or other conditions can be achieved using positive selection steps, as well as negative selection steps against other undesired conditions. in vitro evolution[edit] A similar method of obtaining new deoxyribozymes is through in vitro evolution. Though this term is often used interchangeably with in vitro selection, in vitro evolution more appropriately refers to a slightly different procedure in which the initial oligonucleotide pool is genetically altered over subsequent rounds through genetic recombination or through point mutations.[20][21] For point mutations, the pool can be amplified using error-prone PCR to produce many different strands of various random, single mutations. As with in vitro selection, the evolved strands with increased activity will tend to dominate the pool after multiple selection steps, and once a sufficient catalytic activity is reached, the pool can be sequenced to identify the most active strands. The initial pool for in vitro evolution can be derived from a narrowed subset of sequence space, such as a certain round of an in vitro selection experiment, which is sometimes also called in vitro reselection.[21] The initial pool can also be derived from amplification of a single oligonucleotide strand. As an example of the latter, a recent study showed that a functional deoxyribozyme can be selected through in vitro evolution of a non-catalytic oligonucleotide precursor strand. An arbitrarily chosen DNA
DNA
fragment derived from the m RNA
RNA
transcript of bovine serum albumin was evolved through random point mutations over 25 rounds of selection. Through deep sequencing analysis of various pool generations, the evolution of the most catalytic deoxyribozyme strand could be tracked through each subsequent single mutation.[23] This first successful evolution of catalytic DNA
DNA
from a non-catalytic precursor could provide support for the RNA
RNA
World hypothesis. In another recent study, an RNA
RNA
ligase ribozyme was converted into a deoxyribozyme through in vitro evolution of the inactive deoxyribo-analog of the ribozyme. The new RNA
RNA
ligase deoxyribozyme contained just twelve point mutations, two of which had no effect on activity, and had a catalytic efficiency of approximately 1/10 of the original ribozyme, though the researches hypothesized that the activity could be further increased through further selection.[24] This first evidence for transfer of function between different nucleic acids could provide support for various pre- RNA
RNA
World hypotheses. "True" catalysis?[edit] Because most deoxyribozymes suffer from product inhibition and thus exhibit single-turnover behavior, it is sometimes argued that deoxyribozymes do not exhibit "true" catalytic behavior since they cannot undergo multiple-turnover catalysis like most biological enzymes. However, the general definition of a catalyst requires only that the substance speeds up the rate of a chemical reaction without being consumed by the reaction (i.e. it is not permanently chemically altered and can be recycled). Thus, by this definition, single-turnover deoxyribozymes are indeed catalysts.[5] Furthermore, many endogenous enzymes (both proteins and ribozymes) also exhibit single-turnover behavior,[5] and so the exclusion of deoxyribozymes from the rank of "catalyst" simply because it does not feature multiple-turnover behavior seems unjustified. Applications[edit] Although the discovery of RNA
RNA
enzymes predates that of DNA
DNA
enzymes the latter have some distinct advantages. DNA
DNA
has better cost-effectiveness and DNA
DNA
can be made with longer sequence length and can be made with higher purity in Solid-phase synthesis. Drug clinical trials[edit] Asthma is characterized by eosinophil-induced inflammation motivated by a type 2 helper T cell (Th2). By targeting the transcription factor, GATA3, of the Th2 pathway, with DNAzyme it may be possible to negate the inflammation. The safety and efficacy of SB010, a novel 10-23 DNAzyme was evaluated, and found to have the ability to cleave and inactivate GATA3 messenger RNA
RNA
in phase IIa clinical trials. Treatment with SB010 significantly offset both late and early asthmatic responses after allergen aggravation in male patients with allergic asthma.[25] The transcription factor GATA-3 is also an interesting target, of the DNAzyme topical formulation SB012, for a novel therapeutic strategy in ulcerative colitis (UC). UC is an idiopathic inflammatory bowel diseases defined by chronically relapsing inflammations of the gastrointestinal tract, and characterized by a superficial, continuous mucosal inflammation, which predominantly affects the large intestine. Patients that do not effectively respond to current UC treatment strategies exhibit serious drawbacks one of which may lead to colorectal surgery, and can result in a severely compromised quality of life. Thus, patients with moderate or severe UC may significantly benefit from these new therapeutic alternatives, of which SB012 is in phase I clinical trials.[26] Atopic dermatitis (AD) is a chronic inflammatory skin disorder, in which patients suffer from eczema, often severe pruritus on the affected skin, as well as complications and secondary infections. AD surfaces from an upregulation of Th2-modified immune responses, therefore a novel AD approach using DNAzymes targeting GATA-3 is a plausible treatment option. The topical DNAzyme SB011 is currently in phase II clinical trials.[27] DNAzyme research for the treatment of cancer is also underway. The development of a 10-23 DNAzyme that can block the expression of IGF-I (Insulin-like growth factor I, a contributor to normal cell growth as well as tumorigenesis) by targeting its m RNA
RNA
could be useful for blocking the secretion of IGF-I from prostate storm primary cells ultimately inhibiting prostate tumor development. Additionally, with this treatment it is expected that hepatic metastasis would also be inhibited, via the inhibition of IGF-I in the liver (the major source of serum IGF-I).[28] Sensors[edit] DNAzymes have found practical use in metal biosensors.[29][30] A DNAzyme based biosensor for lead ion was used to detect lead ion in water in St. Paul Public Schools in Minnesota.[31] Asymmetric synthesis[edit] Chirality is another property that a DNAzyme can exploit. DNA
DNA
occurs in nature as a right-handed double helix and in asymmetric synthesis a chiral catalyst is a valuable tool in the synthesis of chiral molecules from an achiral source. In one application an artificial DNA catalyst was prepared by attaching a copper ion to it through a spacer.[32] The copper - DNA
DNA
complex catalysed a Diels-Alder reaction in water between cyclopentadiene and an aza chalcone. The reaction products (endo and exo) were found to be present in an enantiomeric excess of 50%. Later it was found that an enantiomeric excess of 99% could be induced, and that both the rate and the enantioselectivity were related to the DNA
DNA
sequence. Other uses[edit] Other uses of DNA
DNA
in chemistry are in DNA-templated synthesis, Enantioselective catalysis,[33] DNA
DNA
nanowires and DNA
DNA
computing.[34] See also[edit]

Aptamer Ribozyme SELEX

References[edit]

^ a b c Breaker, Ronald R. (May 1997). " DNA
DNA
enzymes". Nature Biotechnology. 15 (5): 427–431. doi:10.1038/nbt0597-427. PMID 9131619.  ^ Kruger, Kelly; Grabowski, Paula J.; Zaug, Arthur J.; Sands, Julie; Gottschling, Daniel E.; Cech, Thomas R. (November 1982). "Self-splicing RNA: Autoexcision and autocyclization of the ribosomal RNA
RNA
intervening sequence of tetrahymena". Cell. 31 (1): 147–157. doi:10.1016/0092-8674(82)90414-7. ISSN 0092-8674. PMID 6297745. Retrieved 2015-07-10.  ^ Guerrier-Takada, Cecilia; Gardiner, Katheleen; Marsh, Terry; Pace, Norman; Altman, Sidney (December 1983). "The RNA
RNA
moiety of ribonuclease P is the catalytic subunit of the enzyme". Cell. 35 (3, Part 2): 849–857. doi:10.1016/0092-8674(83)90117-4. ISSN 0092-8674. PMID 6197186. Retrieved 2015-07-10.  ^ Breaker, Ronald R.; Joyce, Gerald F. (2014-09-18). "The Expanding View of RNA
RNA
and DNA
DNA
Function". Chemistry & Biology. 21 (9): 1059–1065. doi:10.1016/j.chembiol.2014.07.008. ISSN 1074-5521. Retrieved 2015-07-09.  ^ a b c d e f Silverman, Scott K. (2004). "Deoxyribozymes: DNA catalysts for bioorganic chemistry" (PDF). Org. Biomol. Chem. 2 (19): 2701–06. doi:10.1039/B411910J. ISSN 1477-0539. PMID 15455136.  ^ a b c Silverman, Scott K. (2005). "In vitro selection, characterization, and application of deoxyribozymes that cleave RNA". Nucleic Acids Research. 33 (19): 6151–6163. doi:10.1093/nar/gki930. ISSN 0305-1048. PMC 1283523 . PMID 16286368. Retrieved 2015-07-15.  ^ a b Breaker, Ronald R.; Joyce, Gerald F. (December 1994). "A DNA enzyme that cleaves RNA". Chem. Biol. 1 (4): 223–229. doi:10.1016/1074-5521(94)90014-0. PMID 9383394.  ^ Lan, Tian; Furuya, Kimberly; Lu, Yi (2010-06-14). "A highly selective lead sensor based on a classic lead DNAzyme". Chemical Communications. 46 (22): 3896–3898. doi:10.1039/B926910J. ISSN 1364-548X. PMC 3071848 . PMID 20407665. Retrieved 2015-07-30.  ^ Breaker, Ronald R.; Joyce, Gerald F. (1995-01-10). "A DNA
DNA
enzyme with Mg2+-dependent RNA
RNA
phosphoesterase activity". Chemistry & Biology. 2 (10): 655–660. doi:10.1016/1074-5521(95)90028-4. ISSN 1074-5521. PMID 9383471. Retrieved 2015-07-16.  ^ Faulhammer, Dirk; Famulok, Michael (1996-12-01). "The Ca2+ Ion as a Cofactor for a Novel RNA-Cleaving Deoxyribozyme". Angewandte Chemie International Edition in English. 35 (23–24): 2837–2841. doi:10.1002/anie.199628371. ISSN 1521-3773. Retrieved 2015-07-17.  ^ Santoro, Stephen W.; Joyce, Gerald F. (1997-04-29). "A general purpose RNA-cleaving DNA
DNA
enzyme". Proceedings of the National Academy of Sciences. 94 (9): 4262–4266. doi:10.1073/pnas.94.9.4262. ISSN 0027-8424. PMC 20710 . PMID 9113977. Retrieved 2015-07-17.  ^ Cruz, Rani P. G; Withers, Johanna B; Li, Yingfu (January 2004). "Dinucleotide Junction Cleavage Versatility of 8-17 Deoxyribozyme". Chemistry & Biology. 11 (1): 57–67. doi:10.1016/j.chembiol.2003.12.012. ISSN 1074-5521. PMID 15112995. Retrieved 2015-08-13.  ^ Fokina, Alesya A. (Feb 21, 2012). "Targeting Insulin-like Growth Factor I with 10-23 DNAzymes: 2'-O- Methyl
Methyl
Modifications in the Catalytic Core Enhance m RNA
RNA
Cleavage". Journal of the American Chemical Society. 51 (11): 2181–2191. doi:10.1021/bi201532q.  ^ Li, Jing; Lu, Yi (2000-10-01). "A Highly Sensitive and Selective Catalytic DNA
DNA
Biosensor for Lead
Lead
Ions". Journal of the American Chemical Society. 122 (42): 10466–10467. doi:10.1021/ja0021316. ISSN 0002-7863. Retrieved 2015-05-17.  ^ Wu, Peiwen; Hwang, Kevin; Lan, Tian; Lu, Yi (2013-04-10). "A DNAzyme-Gold Nanoparticle Probe for Uranyl
Uranyl
Ion in Living Cells". Journal of the American Chemical Society. 135 (14): 5254–5257. doi:10.1021/ja400150v. ISSN 0002-7863. PMC 3644223 . PMID 23531046.  ^ Torabi, Seyed-Fakhreddin; Wu, Peiwen; McGhee, Claire E.; Chen, Lu; Hwang, Kevin; Zheng, Nan; Cheng, Jianjun; Lu, Yi (2015-05-12). "In vitro selection of a sodium-specific DNAzyme and its application in intracellular sensing". Proceedings of the National Academy of Sciences. 112 (19): 5903–5908. doi:10.1073/pnas.1420361112. ISSN 0027-8424. PMC 4434688 . PMID 25918425. Retrieved 2015-05-17.  ^ Ponce-Salvatierra, Almudena; Wawrzyniak-Turek, Katarzyna; Steuerwald, Ulrich; Höbartner, Claudia; Pena, Vladimir (2016-01-14). "Crystal structure of a DNA
DNA
catalyst". Nature. 529 (7585): 231–234. doi:10.1038/nature16471. ISSN 0028-0836.  ^ Borman, Stu. "After Two Decades Of Trying, Scientists Report First Crystal Structure Of A DNAzyme January 11, 2016 Issue - Vol. 94 Issue 2 Chemical & Engineering News". cen.acs.org. Retrieved 2017-02-04.  ^ Daniel J.-F. Chinnapen; Dipankar Sen (Jan 6, 2004). "A deoxyribozyme that harnesses light to repair thymine dimers in DNA". Proc Natl Acad Sci U S A. US National Library of Medicine: Proceedings of the National Academy of Sciences of the United States of America. 101 (1): 65–9. doi:10.1073/pnas.0305943101. PMC 314139 . PMID 14691255.  ^ a b c Joyce, Gerald F. (2004). "Directed Evolution of Nucleic Acid Enzymes". Annual Review of Biochemistry. 73 (1): 791–836. doi:10.1146/annurev.biochem.73.011303.073717. PMID 15189159. Retrieved 2015-07-27.  ^ a b c d e f g Silverman, Scott K. (2008-07-23). "Catalytic DNA (deoxyribozymes) for synthetic applications—current abilities and future prospects". Chemical Communications (30): 3467–3485. doi:10.1039/B807292M. ISSN 1364-548X. Retrieved 2015-07-27.  ^ Spill F; Weinstein ZB; Shemirani AI; Ho N; Desai D; Zaman MH (2016). "Controlling uncertainty in aptamer selection". PNAS. 113 (43): 12076–12081. doi:10.1073/pnas.1605086113. PMC 5087011 . PMID 27790993.  ^ Gysbers, Rachel; Tram, Kha; Gu, Jimmy; Li, Yingfu (2015-06-19). "Evolution of an Enzyme
Enzyme
from a Noncatalytic Nucleic Acid Sequence". Scientific Reports. 5: 11405. doi:10.1038/srep11405. PMC 4473686 . PMID 26091540. Retrieved 2015-07-15.  ^ Paul, Natasha; Springsteen, Greg; Joyce, Gerald F. (March 2006). "Conversion of a Ribozyme
Ribozyme
to a Deoxyribozyme
Deoxyribozyme
through In Vitro Evolution". Chemistry & Biology. 13 (3): 329–338. doi:10.1016/j.chembiol.2006.01.007. ISSN 1074-5521. PMID 16638538. Retrieved 2015-07-20.  ^ Krug, N (May 21, 2015). "Allergen-induced asthmatic responses modified by a GATA3-specific DNAzyme". New England Journal of Medicine. 372 (21): 1987–1995. doi:10.1056/nejmoa1411776. PMID 25981191.  ^ "Efficacy, Pharmacokinetics, Tolerability, Safety of SB012 Intrarectally Applied in Active Ulcerative Colitis Patients (SECURE)". ClinicalTrials.gov. Retrieved May 27, 2016.  ^ "Efficacy, Safety, Tolerability, Pharmacokinetics and Pharmacodynamics Study of the Topical Formulation SB011 Applied to Lesional Skin in Patients With Atopic Eczema". ClinicalTrail.gov. Retrieved May 27, 2016.  ^ Fokina, Alesya (Feb 21, 2012). "Targeting Insulin-like Growth Factor I with 10-23 DNAzymes: 2'-O- Methyl
Methyl
Modifications in the Catalytic Core Enhance m RNA
RNA
Cleavage". Journal of the American Chemical Society. 51 (11): 2181–2191. doi:10.1021/bi201532q.  ^ Juewen Liu; Yi Lu (2004). "Optimization of a Pb2+-Directed Gold Nanoparticle/DNAzyme Assembly and Its Application as a Colorimetric Biosensor for Pb2+". Chem. Mater. 16 (17): 3231–38. doi:10.1021/cm049453j.  ^ Wei, Hui; Li, Bingling; Li, Jing; Dong, Shaojun; Wang, Erkang (2008-01-01). "DNAzyme-based colorimetric sensing of lead (Pb 2+ ) using unmodified gold nanoparticle probes". Nanotechnology. 19 (9): 095501. doi:10.1088/0957-4484/19/9/095501. ISSN 0957-4484. PMID 21817668.  ^ " Lead
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in Water: St. Paul Schools Delayed Fixes". ABC 6 NEWS. Retrieved 2017-02-04.  ^ Gerard Roelfes; Ben L. Feringa (2005). "DNA-Based Asymmetric Catalysis". Angewandte Chemie International Edition. 44 (21): 3230–2. doi:10.1002/anie.200500298. PMID 15844122.  ^ García-Fernández, Almudena; Roelfez, Gerard (2012). "Chapter 9. Enantioselective catalysis at the DNA
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Scaffold". In Astrid Sigel, Helmut Sigel and Roland K. O. Sigel. Interplay between Metal Ions and Nucleic Acids. Metal Ions in Life Sciences. 10. Springer. pp. 249–268. doi:10.1007/978-94-007-2172-2_9.  ^ Yoshihiro Ito; Eiichiro Fukusaki (2004). " DNA
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B: Enzymatic. 28 (4–6): 155–166. doi:10.1016/j.molcatb.2004.01.016. Archived from the original (PDF) on 2005-10-28. 

External links[edit]

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The Info List - Deoxyribozyme


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Deoxyribozymes, also called DNA
DNA
enzymes, DNAzymes, or catalytic DNA, are DNA
DNA
oligonucleotides that are capable of performing a specific chemical reaction, often but not always catalytic. This is similar to the action of other biological enzymes, such as proteins or ribozymes (enzymes composed of RNA).[1] However, in contrast to the abundance of protein enzymes in biological systems and the discovery of biological ribozymes in the 1980s,[2][3] there are no known naturally occurring deoxyribozymes.[4] Deoxyribozymes should not be confused with DNA aptamers which are oligonucleotides that selectively bind a target ligand, but do not catalyze a subsequent chemical reaction. With the exception of ribozymes, nucleic acid molecules within cells primarily serve as storage of genetic information due to its ability to form complementary base pairs, which allows for high-fidelity copying and transfer of genetic information. In contrast, nucleic acid molecules are more limited in their catalytic ability, in comparison to protein enzymes, to just three types of interactions: hydrogen bonding, pi stacking, and metal-ion coordination. This is due to the limited number of functional groups of the nucleic acid monomers: while proteins are built from up to twenty different amino acids with various functional groups, nucleic acids are built from just four chemically similar nucleobases. In addition, DNA
DNA
lacks the 2'-hydroxyl group found in RNA
RNA
which limits the catalytic competency of deoxyribozymes even in comparison to ribozymes.[5] In addition to the inherent inferiority of DNA
DNA
catalytic activity, the apparent lack of naturally occurring deoxyribozymes may also be due to the primarily double-stranded conformation of DNA
DNA
in biological systems which would limit its physical flexibility and ability to form tertiary structures, and so would drastically limit the ability of double-stranded DNA
DNA
to act as a catalyst;[5] though there are a few known instances of biological single-stranded DNA
DNA
such as multicopy single-stranded DNA
DNA
(msDNA), certain viral genomes, and the replication fork formed during DNA
DNA
replication. Further structural differences between DNA
DNA
and RNA
RNA
may also play a role in the lack of biological deoxyribozymes, such as the additional methyl group of the DNA
DNA
base thymidine compared to the RNA
RNA
base uracil or the tendency of DNA
DNA
to adopt the B-form helix while RNA
RNA
tends to adopt the A-form helix.[1] However, it has also been shown that DNA
DNA
can form structures that RNA
RNA
cannot, which suggests that, though there are differences in structures that each can form, neither is inherently more or less catalytic due to their possible structural motifs.[1]

Contents

1 Types

1.1 Ribonucleases 1.2 RNA
RNA
ligases 1.3 Other reactions

2 Methods

2.1 in vitro selection 2.2 in vitro evolution

3 "True" catalysis? 4 Applications

4.1 Drug clinical trials 4.2 Sensors 4.3 Asymmetric synthesis 4.4 Other uses

5 See also 6 References 7 External links

Types[edit] Ribonucleases[edit]

The trans-form (two separate strands) of the 17E DNAzyme. Most ribonuclease DNAzymes have a similar form, consisting of a separate enzyme strand (blue/cyan) and substrate strand (black). Two arms of complementary bases flank the catalytic core (cyan) on the enzyme strand and the single ribonucleotide (red) on the substrate strand. The arrow shows the ribonucleotide cleavage site.

The most abundant class of deoxyribozymes are ribonucleases, which catalyze the cleavage of a ribonucleotide phosphodiester bond through a transesterification reaction, forming a 2'3'-cyclic phosphate terminus and a 5'-hydroxyl terminus.[5][6] Ribonuclease
Ribonuclease
deoxyribozymes typically undergo selection as long, single-stranded oligonucleotides which contain a single ribonucleotide base to act as the cleavage site. Once sequenced, this single-stranded "cis"-form of the deoxyribozyme can be converted to the two-stranded "trans"-form by separating the substrate domain (containing the ribonucleotide cleavage site) and the enzyme domain (containing the catalytic core) into separate strands which can hybridize through two flanking arms consisting of complementary base pairs. The first known deoxyribozyme was a ribonuclease, discovered in 1994 by Ronald Breaker while a postdoctoral fellow in the laboratory of Gerald Joyce
Gerald Joyce
at the Scripps Research Institute.[7] This deoxyribozyme, later named GR-5,[8] catalyzes the Pb2+-dependent cleavage of a single ribonucleotide phosphoester at a rate that is more than 100-fold compared to the uncatalyzed reaction.[7] Subsequently, additional RNA-cleaving deoxyribozymes that incorporate different metal cofactors were developed, including the Mg2+-dependent E2 deoxyribozyme[9] and the Ca2+-dependent Mg5 deoxyribozyme.[10] These first deoxyribozymes were unable to catalyze a full RNA
RNA
substrate strand, but by incorporating the full RNA
RNA
substrate strand into the selection process, deoxyribozymes which functioned with substrates consisting of either full RNA
RNA
or full DNA
DNA
with a single RNA
RNA
base were both able to be utilized.[11] The first of these more versatile deoxyribozymes, 8-17 and 10-23, are currently the most widely studied deoxyribozymes. In fact, many subsequently discovered deoxyribozymes were found to contain the same catalytic core motif as 8-17, including the previously discovered Mg5, suggesting that this motif represents the "simplest solution for the RNA
RNA
cleavage problem".[6][12] The 10-23 DNAzyme contains a 15-nucleotide catalytic core that is flanked by two substrate recognition domains. This DNAzyme cleaves complementary RNAs efficiently in a sequence specific manner between an unpaired purine and a paired pyrimidine. DNAzymes targeting AU or GU vs. GC or AC are more effective. Furthermore, the RNA
RNA
cleavage rates have been shown to increase after the introduction of intercalators or the substitution of deoxyguanine with deoxyinosine at the junction of the catalytic loop. Specifically, the addition of 2’-O-methyl modifications to the catalytic proved to significantly increase the cleavage rate both in vitro and in vivo. [13] Other notable deoxyribozyme ribonucleases are those that are highly selective for a certain cofactor. Among this group are the metal selective deoxyribozymes such as Pb2+-specific 17E,[14] UO22+-specific 39E,[15] and Na+-specific A43.[16] First crystal structure of a DNAzyme was reported in 2016.[17][18] RNA
RNA
ligases[edit] Of particular interest are DNA
DNA
ligases.[5] These molecules have demonstrated remarkable chemoselectivity in RNA
RNA
branching reactions. Although each repeating unit in a RNA
RNA
strand owns a free hydroxyl group, the DNA
DNA
ligase takes just one of them as a branching starting point. An accomplishment unattainable with traditional organic chemistry. Other reactions[edit] Many other deoxyribozymes have since been developed that catalyze DNA phosphorylation, DNA
DNA
adenylation, DNA
DNA
deglycosylation, porphyrin metalation, thymine dimer photoreversion[19] and DNA
DNA
cleavage. Methods[edit] Main article: Systematic evolution of ligands by exponential enrichment in vitro selection[edit] Because there are no known naturally occurring deoxyribozymes, most known deoxyribozyme sequences have been discovered through a high-throughput in vitro selection technique, similar to SELEX.[20][21] in vitro selection utilizes a "pool" of a large number of random DNA
DNA
sequences (typically 1014–1015 unique strands) that can be screened for a specific catalytic activity. The pool is synthesized through solid phase synthesis such that each strand has two constant regions (primer binding sites for PCR amplification) flanking a random region of a certain length, typically 25–50 bases long. Thus the total number of unique strands, called the sequence space, is 4N where N denotes the number of bases in the random region. Because 425 ≈ 1015, there is no practical reason to choose random regions of less than 25 bases in length, while going above this number of bases means that the total sequence space cannot be surveyed. However, since there are likely many potential candidates for a given catalytic reaction within the sequence space, random regions of 50 and even higher have successfully yielded catalytic deoxyribozymes.[21] The pool is first subjected to a selection step, during which the catalytic strands are separated from the non-catalytic strands. The exact separation method will depend on the reaction being catalyzed. As an example, the separation step for ribonucleotide cleavage often utilizes affinity chromatography, in which a biological tag attached to each DNA
DNA
strand is removed from any catalytically active strands via cleavage of a ribonucleotide base. This allows the catalytic strands to be separated by a column that specifically binds the tag, since the non-active strands will remain bound to the column while the active strands (which no longer possess the tag) flow through. A common set-up for this is a biotin tag with a streptavidin affinity column.[20][21] Gel electrophoresis based separation can also be used in which the change in molecular weight of strands upon the cleavage reaction is enough to cause a shift in the location of the reactive strands on the gel.[21] After the selection step, the reactive pool is amplified via polymerase chain reaction (PCR) to regenerate and amplify the reactive strands, and the process is repeated until a pool of sufficient reactivity is obtained. Multiple rounds of selection are required because some non-catalytic strands will inevitably make it through any single selection step. Usually 4–10 rounds are required for unambiguous catalytic activity,[6] though more rounds are often necessary for more stringent catalytic conditions. After a sufficient number of rounds, the final pool is sequenced and the individual strands are tested for their catalytic activity.[21] The dynamics of the pool can be described through mathematical modeling [22] , which shows how oligonucleotides undergo competitive binding with the targets and how the evolutionary outcome can be improved through fine tuning of parameters. Deoxyribozymes obtained through in vitro selection will be optimized for the conditions during the selection, such as salt concentration, pH, and the presence of cofactors. Because of this, catalytic activity only in the presence of specific cofactors or other conditions can be achieved using positive selection steps, as well as negative selection steps against other undesired conditions. in vitro evolution[edit] A similar method of obtaining new deoxyribozymes is through in vitro evolution. Though this term is often used interchangeably with in vitro selection, in vitro evolution more appropriately refers to a slightly different procedure in which the initial oligonucleotide pool is genetically altered over subsequent rounds through genetic recombination or through point mutations.[20][21] For point mutations, the pool can be amplified using error-prone PCR to produce many different strands of various random, single mutations. As with in vitro selection, the evolved strands with increased activity will tend to dominate the pool after multiple selection steps, and once a sufficient catalytic activity is reached, the pool can be sequenced to identify the most active strands. The initial pool for in vitro evolution can be derived from a narrowed subset of sequence space, such as a certain round of an in vitro selection experiment, which is sometimes also called in vitro reselection.[21] The initial pool can also be derived from amplification of a single oligonucleotide strand. As an example of the latter, a recent study showed that a functional deoxyribozyme can be selected through in vitro evolution of a non-catalytic oligonucleotide precursor strand. An arbitrarily chosen DNA
DNA
fragment derived from the m RNA
RNA
transcript of bovine serum albumin was evolved through random point mutations over 25 rounds of selection. Through deep sequencing analysis of various pool generations, the evolution of the most catalytic deoxyribozyme strand could be tracked through each subsequent single mutation.[23] This first successful evolution of catalytic DNA
DNA
from a non-catalytic precursor could provide support for the RNA
RNA
World hypothesis. In another recent study, an RNA
RNA
ligase ribozyme was converted into a deoxyribozyme through in vitro evolution of the inactive deoxyribo-analog of the ribozyme. The new RNA
RNA
ligase deoxyribozyme contained just twelve point mutations, two of which had no effect on activity, and had a catalytic efficiency of approximately 1/10 of the original ribozyme, though the researches hypothesized that the activity could be further increased through further selection.[24] This first evidence for transfer of function between different nucleic acids could provide support for various pre- RNA
RNA
World hypotheses. "True" catalysis?[edit] Because most deoxyribozymes suffer from product inhibition and thus exhibit single-turnover behavior, it is sometimes argued that deoxyribozymes do not exhibit "true" catalytic behavior since they cannot undergo multiple-turnover catalysis like most biological enzymes. However, the general definition of a catalyst requires only that the substance speeds up the rate of a chemical reaction without being consumed by the reaction (i.e. it is not permanently chemically altered and can be recycled). Thus, by this definition, single-turnover deoxyribozymes are indeed catalysts.[5] Furthermore, many endogenous enzymes (both proteins and ribozymes) also exhibit single-turnover behavior,[5] and so the exclusion of deoxyribozymes from the rank of "catalyst" simply because it does not feature multiple-turnover behavior seems unjustified. Applications[edit] Although the discovery of RNA
RNA
enzymes predates that of DNA
DNA
enzymes the latter have some distinct advantages. DNA
DNA
has better cost-effectiveness and DNA
DNA
can be made with longer sequence length and can be made with higher purity in Solid-phase synthesis. Drug clinical trials[edit] Asthma is characterized by eosinophil-induced inflammation motivated by a type 2 helper T cell (Th2). By targeting the transcription factor, GATA3, of the Th2 pathway, with DNAzyme it may be possible to negate the inflammation. The safety and efficacy of SB010, a novel 10-23 DNAzyme was evaluated, and found to have the ability to cleave and inactivate GATA3 messenger RNA
RNA
in phase IIa clinical trials. Treatment with SB010 significantly offset both late and early asthmatic responses after allergen aggravation in male patients with allergic asthma.[25] The transcription factor GATA-3 is also an interesting target, of the DNAzyme topical formulation SB012, for a novel therapeutic strategy in ulcerative colitis (UC). UC is an idiopathic inflammatory bowel diseases defined by chronically relapsing inflammations of the gastrointestinal tract, and characterized by a superficial, continuous mucosal inflammation, which predominantly affects the large intestine. Patients that do not effectively respond to current UC treatment strategies exhibit serious drawbacks one of which may lead to colorectal surgery, and can result in a severely compromised quality of life. Thus, patients with moderate or severe UC may significantly benefit from these new therapeutic alternatives, of which SB012 is in phase I clinical trials.[26] Atopic dermatitis (AD) is a chronic inflammatory skin disorder, in which patients suffer from eczema, often severe pruritus on the affected skin, as well as complications and secondary infections. AD surfaces from an upregulation of Th2-modified immune responses, therefore a novel AD approach using DNAzymes targeting GATA-3 is a plausible treatment option. The topical DNAzyme SB011 is currently in phase II clinical trials.[27] DNAzyme research for the treatment of cancer is also underway. The development of a 10-23 DNAzyme that can block the expression of IGF-I (Insulin-like growth factor I, a contributor to normal cell growth as well as tumorigenesis) by targeting its m RNA
RNA
could be useful for blocking the secretion of IGF-I from prostate storm primary cells ultimately inhibiting prostate tumor development. Additionally, with this treatment it is expected that hepatic metastasis would also be inhibited, via the inhibition of IGF-I in the liver (the major source of serum IGF-I).[28] Sensors[edit] DNAzymes have found practical use in metal biosensors.[29][30] A DNAzyme based biosensor for lead ion was used to detect lead ion in water in St. Paul Public Schools in Minnesota.[31] Asymmetric synthesis[edit] Chirality is another property that a DNAzyme can exploit. DNA
DNA
occurs in nature as a right-handed double helix and in asymmetric synthesis a chiral catalyst is a valuable tool in the synthesis of chiral molecules from an achiral source. In one application an artificial DNA catalyst was prepared by attaching a copper ion to it through a spacer.[32] The copper - DNA
DNA
complex catalysed a Diels-Alder reaction in water between cyclopentadiene and an aza chalcone. The reaction products (endo and exo) were found to be present in an enantiomeric excess of 50%. Later it was found that an enantiomeric excess of 99% could be induced, and that both the rate and the enantioselectivity were related to the DNA
DNA
sequence. Other uses[edit] Other uses of DNA
DNA
in chemistry are in DNA-templated synthesis, Enantioselective catalysis,[33] DNA
DNA
nanowires and DNA
DNA
computing.[34] See also[edit]

Aptamer Ribozyme SELEX

References[edit]

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DNA
enzymes". Nature Biotechnology. 15 (5): 427–431. doi:10.1038/nbt0597-427. PMID 9131619.  ^ Kruger, Kelly; Grabowski, Paula J.; Zaug, Arthur J.; Sands, Julie; Gottschling, Daniel E.; Cech, Thomas R. (November 1982). "Self-splicing RNA: Autoexcision and autocyclization of the ribosomal RNA
RNA
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RNA
moiety of ribonuclease P is the catalytic subunit of the enzyme". Cell. 35 (3, Part 2): 849–857. doi:10.1016/0092-8674(83)90117-4. ISSN 0092-8674. PMID 6197186. Retrieved 2015-07-10.  ^ Breaker, Ronald R.; Joyce, Gerald F. (2014-09-18). "The Expanding View of RNA
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and DNA
DNA
Function". Chemistry & Biology. 21 (9): 1059–1065. doi:10.1016/j.chembiol.2014.07.008. ISSN 1074-5521. Retrieved 2015-07-09.  ^ a b c d e f Silverman, Scott K. (2004). "Deoxyribozymes: DNA catalysts for bioorganic chemistry" (PDF). Org. Biomol. Chem. 2 (19): 2701–06. doi:10.1039/B411910J. ISSN 1477-0539. PMID 15455136.  ^ a b c Silverman, Scott K. (2005). "In vitro selection, characterization, and application of deoxyribozymes that cleave RNA". Nucleic Acids Research. 33 (19): 6151–6163. doi:10.1093/nar/gki930. ISSN 0305-1048. PMC 1283523 . PMID 16286368. Retrieved 2015-07-15.  ^ a b Breaker, Ronald R.; Joyce, Gerald F. (December 1994). "A DNA enzyme that cleaves RNA". Chem. Biol. 1 (4): 223–229. doi:10.1016/1074-5521(94)90014-0. PMID 9383394.  ^ Lan, Tian; Furuya, Kimberly; Lu, Yi (2010-06-14). "A highly selective lead sensor based on a classic lead DNAzyme". Chemical Communications. 46 (22): 3896–3898. doi:10.1039/B926910J. ISSN 1364-548X. PMC 3071848 . PMID 20407665. Retrieved 2015-07-30.  ^ Breaker, Ronald R.; Joyce, Gerald F. (1995-01-10). "A DNA
DNA
enzyme with Mg2+-dependent RNA
RNA
phosphoesterase activity". Chemistry & Biology. 2 (10): 655–660. doi:10.1016/1074-5521(95)90028-4. ISSN 1074-5521. PMID 9383471. Retrieved 2015-07-16.  ^ Faulhammer, Dirk; Famulok, Michael (1996-12-01). "The Ca2+ Ion as a Cofactor for a Novel RNA-Cleaving Deoxyribozyme". Angewandte Chemie International Edition in English. 35 (23–24): 2837–2841. doi:10.1002/anie.199628371. ISSN 1521-3773. Retrieved 2015-07-17.  ^ Santoro, Stephen W.; Joyce, Gerald F. (1997-04-29). "A general purpose RNA-cleaving DNA
DNA
enzyme". Proceedings of the National Academy of Sciences. 94 (9): 4262–4266. doi:10.1073/pnas.94.9.4262. ISSN 0027-8424. PMC 20710 . PMID 9113977. Retrieved 2015-07-17.  ^ Cruz, Rani P. G; Withers, Johanna B; Li, Yingfu (January 2004). "Dinucleotide Junction Cleavage Versatility of 8-17 Deoxyribozyme". Chemistry & Biology. 11 (1): 57–67. doi:10.1016/j.chembiol.2003.12.012. ISSN 1074-5521. PMID 15112995. Retrieved 2015-08-13.  ^ Fokina, Alesya A. (Feb 21, 2012). "Targeting Insulin-like Growth Factor I with 10-23 DNAzymes: 2'-O- Methyl
Methyl
Modifications in the Catalytic Core Enhance m RNA
RNA
Cleavage". Journal of the American Chemical Society. 51 (11): 2181–2191. doi:10.1021/bi201532q.  ^ Li, Jing; Lu, Yi (2000-10-01). "A Highly Sensitive and Selective Catalytic DNA
DNA
Biosensor for Lead
Lead
Ions". Journal of the American Chemical Society. 122 (42): 10466–10467. doi:10.1021/ja0021316. ISSN 0002-7863. Retrieved 2015-05-17.  ^ Wu, Peiwen; Hwang, Kevin; Lan, Tian; Lu, Yi (2013-04-10). "A DNAzyme-Gold Nanoparticle Probe for Uranyl
Uranyl
Ion in Living Cells". Journal of the American Chemical Society. 135 (14): 5254–5257. doi:10.1021/ja400150v. ISSN 0002-7863. PMC 3644223 . PMID 23531046.  ^ Torabi, Seyed-Fakhreddin; Wu, Peiwen; McGhee, Claire E.; Chen, Lu; Hwang, Kevin; Zheng, Nan; Cheng, Jianjun; Lu, Yi (2015-05-12). "In vitro selection of a sodium-specific DNAzyme and its application in intracellular sensing". Proceedings of the National Academy of Sciences. 112 (19): 5903–5908. doi:10.1073/pnas.1420361112. ISSN 0027-8424. PMC 4434688 . PMID 25918425. Retrieved 2015-05-17.  ^ Ponce-Salvatierra, Almudena; Wawrzyniak-Turek, Katarzyna; Steuerwald, Ulrich; Höbartner, Claudia; Pena, Vladimir (2016-01-14). "Crystal structure of a DNA
DNA
catalyst". Nature. 529 (7585): 231–234. doi:10.1038/nature16471. ISSN 0028-0836.  ^ Borman, Stu. "After Two Decades Of Trying, Scientists Report First Crystal Structure Of A DNAzyme January 11, 2016 Issue - Vol. 94 Issue 2 Chemical & Engineering News". cen.acs.org. Retrieved 2017-02-04.  ^ Daniel J.-F. Chinnapen; Dipankar Sen (Jan 6, 2004). "A deoxyribozyme that harnesses light to repair thymine dimers in DNA". Proc Natl Acad Sci U S A. US National Library of Medicine: Proceedings of the National Academy of Sciences of the United States of America. 101 (1): 65–9. doi:10.1073/pnas.0305943101. PMC 314139 . PMID 14691255.  ^ a b c Joyce, Gerald F. (2004). "Directed Evolution of Nucleic Acid Enzymes". Annual Review of Biochemistry. 73 (1): 791–836. doi:10.1146/annurev.biochem.73.011303.073717. PMID 15189159. Retrieved 2015-07-27.  ^ a b c d e f g Silverman, Scott K. (2008-07-23). "Catalytic DNA (deoxyribozymes) for synthetic applications—current abilities and future prospects". Chemical Communications (30): 3467–3485. doi:10.1039/B807292M. ISSN 1364-548X. Retrieved 2015-07-27.  ^ Spill F; Weinstein ZB; Shemirani AI; Ho N; Desai D; Zaman MH (2016). "Controlling uncertainty in aptamer selection". PNAS. 113 (43): 12076–12081. doi:10.1073/pnas.1605086113. PMC 5087011 . PMID 27790993.  ^ Gysbers, Rachel; Tram, Kha; Gu, Jimmy; Li, Yingfu (2015-06-19). "Evolution of an Enzyme
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Methyl
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RNA
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External links[edit]

Deoxyribozyme
Deoxyribozyme
at the US National Library of Medicine Medical Subject Headings (MeSH)

v t e

Types of nucleic acids

Constituents

Nucleobases Nucleosides Nucleotides Deoxynucleotides

Ribonucleic acids (coding, non-coding)

Translational

Messenger

precursor, heterogenous nuclear

Transfer Ribosomal Transfer-messenger

Regulatory

Interferential

Micro Small interfering Piwi-interacting

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Small nuclear Small nucleolar Small Cajal Body RNAs Y RNA

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Guide Ribozyme Small hairpin Small temporal Trans-acting small interfering Subgenomic messenger

Deoxyribonucleic acids

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