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CRISPR RNA
CRISPR RNA or crRNA is a RNA transcript from the CRISPR locus. CRISPR-Cas (clustered, regularly interspaced short palindromic repeats - CRISPR associated systems) is an adaptive immune system found in bacteria and archaea to protect against mobile genetic elements, like viruses, plasmids, and Transposable element, transposons. The CRISPR locus contains a series of repeats interspaced with unique spacers. These unique spacers can be acquired from Mobile genetic elements, MGEs. Pre-crRNA is formed after the transcription of the CRISPR locus and before being processed by Cas proteins. Mature crRNA transcripts contain a partial conserved section of repeat and a sequence of spacer that is complementary to the target DNA. crRNA forms an effector complex with a single nuclease or multiple Cas proteins called a Cascade (CRISPR-associated complex for antiviral defense). Once the effector complex is formed a Cas nuclease or single effector protein will cause interference guided by the crRN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Transcript
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs). mRNA comprises only 1–3% of total RNA samples. Less than 2% of the human genome can be transcribed into mRNA ( Human genome#Coding vs. noncoding DNA), while at least 80% of mammalian genomic DNA can be actively transcribed (in one or more types of cells), with the majority of this 80% considered to be ncRNA. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. Transcription proceeds in the following general steps: # RNA polymerase, together with one or more general transcription factors, binds to promoter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helicase
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands (hence '' helic- + -ase''), using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases. The human genome codes for 95 non-redundant helicases: 64 RNA helicases and 31 DNA helicases. Many cellular processes, such as DNA replication, transcription, translation, recombination, DNA repair, and ribosome biogenesis involve the separation of nucleic acid strands that necessitates the use of helicases. Some specialized helicases are also involved in sensing of viral nucleic acids during infection and fulfill a immunological function. Function Helicases are o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas12a
Cas12a (CRISPR associated protein 12a, previously known as Cpf1) is an RNA-guided endonuclease of that forms part of the CRISPR system in some bacteria and is used by scientists to modify DNA. It originates as part of a bacterial immune mechanism, where it serves to destroy the genetic material of viruses and thus protect the cell and colony from viral infection. Cas12a and other CRISPR associated endonucleases are unique in that their use of a guide RNA makes this action highly selective; they only cut DNA when it is adjacent to a certain sequence of nucleotides. In the organisms from which it originates, this guide RNA is a copy of a piece of the genome from a virus that previously infected the cell. It is of interest to researchers because it can be used to make highly targeted modifications of DNA or RNA, similar to the better known CRISPR/ Cas9 system. Cas12a is distinguished from Cas9 by being smaller and simpler, not requiring a tracrRNA, and creating sticky rather t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prophage
A prophage is a bacteriophage (often shortened to "phage") genome that is integrated into the circular bacterial chromosome or exists as an extrachromosomal plasmid within the bacterial cell. Integration of prophages into the bacterial host is the characteristic step of the lysogenic cycle of temperate phages. Prophages remain latent in the genome through multiple cell divisions until activation by an external factor, such as UV light, leading to production of new phage particles that will lyse the cell and spread. As ubiquitous mobile genetic elements, prophages play important roles in bacterial genetics and evolution, such as in the acquisition of virulence factors. Background Prophages are able to do a multitude of things within their respective bacterial strains. Prophages can increase the virulence potential of bacterial strains in both humans and plant pathogens as well as increase the ability of the bacteria to survive in harsh environments. Pathogens have been able to adap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Stages Of CRISPR Immunity
''The'' () is a grammatical article in English, denoting persons or things that are already or about to be mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with nouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a consonant sound, and as (homophone of the archaic pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protospacer Adjacent Motif
A protospacer adjacent motif (PAM) is a 2–6-base pair DNA sequence immediately following the DNA sequence targeted by the Cas9 nuclease in the CRISPR bacterial adaptive immune system. The PAM is a component of the invading virus or plasmid, but is not found in the bacterial host genome and hence is not a component of the bacterial CRISPR#Locus structure, CRISPR locus. Cas9 will not successfully bind to or cleave the target DNA sequence if it is not followed by the PAM sequence. PAM is an essential targeting component which distinguishes bacterial self from non-self DNA, thereby preventing the CRISPR locus from being targeted and destroyed by the CRISPR-associated nuclease. Spacers/protospacers In a bacterial genome, CRISPR loci contain "spacers" (viral DNA inserted into a CRISPR locus) that in CRISPR#Cas genes and CRISPR subtypes, type II adaptive immune systems were created from invading viral or plasmid DNA (called "protospacers"). Upon subsequent invasion, a CRISPR-associated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guide RNA
A guide RNA (gRNA) is a piece of RNA that functions as a guide for RNA- or DNA-targeting enzymes, with which it forms complexes. Very often these enzymes will delete, insert or otherwise alter the targeted RNA or DNA. They occur naturally, serving important functions, but can also be designed to be used for targeted editing, such as with CRISPR-Cas9 and CRISPR-Cas12. History RNA-editing Guide RNA was discovered in 1990 by B. Blum, N. Bakalara, and L. Simpson in the mitochondria of protists called Leishmania tarentolae. The guide RNA there is encoded in maxicircle DNA and contains sequences matching those within the edited regions of the mRNA. They enable the cleavage, insertion and deletion of bases. Guide RNA in Protists Trypanosomatid protists and other kinetoplastids have a novel post-transcriptional mitochondrial RNA modification process known as "RNA editing". They have a large segment of highly organized DNA segments in their mitochondria. This mitochondrial DNA is circul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trans-activating CrRNA
In molecular biology, trans-activating crispr RNA (tracrRNA) is a small ''trans''-encoded RNA. It was first discovered by Emmanuelle Charpentier in her study of human pathogen ''Streptococcus pyogenes'', a type of bacteria that causes harm to humanity. In bacteria and archaea; CRISPR-Cas (clustered, regularly interspaced short palindromic repeats/CRISPR-associated proteins) constitute an RNA-mediated defense system which protects against viruses and plasmids. This defensive pathway has three steps. First a copy of the invading nucleic acid is integrated into the CRISPR locus. Next, CRISPR RNAs ( crRNAs) are transcribed from this CRISPR locus. The crRNAs are then incorporated into effector complexes, where the crRNA guides the complex to the invading nucleic acid and the Cas proteins degrade this nucleic acid. There are several CRISPR system subtypes. Type II CRISPR-Cas systems require a tracrRNA which plays a role in the maturation of crRNA. The tracrRNA is partially complementa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas9
Cas9 (CRISPR associated protein 9, formerly called Cas5, Csn1, or Csx12) is a 160 kilodalton protein which plays a vital role in the immunological defense of certain bacteria against DNA viruses and plasmids, and is heavily utilized in genetic engineering applications. Its main function is to cut DNA and thereby alter a cell's genome. The CRISPR-Cas9 genome editing technique was a significant contributor to the Nobel Prize in Chemistry in 2020 being awarded to Emmanuelle Charpentier and Jennifer Doudna. More technically, Cas9 is a dual RNA-guided DNA endonuclease enzyme associated with the Clustered Regularly Interspaced Short Palindromic Repeats ( CRISPR) adaptive immune system in ''Streptococcus pyogenes''. ''S. pyogenes'' utilizes CRISPR to memorize and Cas9 to later interrogate and cleave foreign DNA, such as invading bacteriophage DNA or plasmid DNA. Cas9 performs this interrogation by unwinding foreign DNA and checking for sites complementary to the 20 nucleotide spacer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cas3
Cas3 is an ATP-dependent single-strand DNA (ssDNA) translocase/helicase enzyme that degrades DNA as part of CRISPR based immunity. Cas3 is a "signature" protein of class 1 CRISPR systems and functions in a complex known as CASCADE, with other cas genes and a targeting RNA to degrade viral DNA. In April 2019 Cornell University researcher Ailong Ke published a paper in the journal ''Molecular Cell'' describing a new gene editing CRISPR system, CRISPR-Cas3 which can efficiently delete long swaths of DNA from a targeted site in the human genome. This ability is superior to that achieved with the more common CRISPR-Cas9 Cas9 (CRISPR associated protein 9, formerly called Cas5, Csn1, or Csx12) is a 160 kilodalton protein which plays a vital role in the immunological defense of certain bacteria against DNA viruses and plasmids, and is heavily utilized in genetic ... systems. CONAN, a CRISPR based diagnostic approach was developed utilising Cas3 References Enzymes Immune s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CRISPR-Cas
CRISPR () (an acronym for clustered regularly interspaced short palindromic repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from DNA fragments of bacteriophages that had previously infected the prokaryote. They are used to detect and destroy DNA from similar bacteriophages during subsequent infections. Hence these sequences play a key role in the antiviral (i.e. anti-phage) defense system of prokaryotes and provide a form of acquired immunity. CRISPR is found in approximately 50% of sequenced bacterial genomes and nearly 90% of sequenced archaea. Cas9 (or "CRISPR-associated protein 9") is an enzyme that uses CRISPR sequences as a guide to recognize and cleave specific strands of DNA that are complementary to the CRISPR sequence. Cas9 enzymes together with CRISPR sequences form the basis of a technology known as CRISPR-Cas9 that can be used to edit genes within organisms. This editin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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