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DNA End Resection
DNA end resection, also called 5′–3′ degradation, is a biochemical process where the blunt end of a section of double-stranded DNA (dsDNA) is modified by cutting away some nucleotides from the 5' end to produce a 3' single-stranded sequence. The presence of a section of single-stranded DNA (ssDNA) allows the broken end of the DNA to line up accurately with a matching sequence, so that it can be accurately repaired.Double-strand breaks (DSBs) can occur at any phase of the cell cycle causing DNA end resection and repair activities to take place, but they are also normal intermediates in mitosis recombination. Furthermore, the natural ends of the linear chromosomes resemble DSBs, and although DNA breaks can cause damage to the integrity of genomic DNA, the natural ends are packed into complex specialized DNA protective packages called telomeres that prevent DNA repair activities. Telomeres and mitotic DSBs have different functionality, but both experience the same 5′–3′ d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sticky And Blunt Ends
DNA ends refer to the properties of the ends of linear DNA molecules, which in molecular biology are described as "sticky" or "blunt" based on the shape of the complementary strands at the terminus. In sticky ends, one strand is longer than the other (typically by at least a few nucleotides), such that the longer strand has bases which are left unpaired. In blunt ends, both strands are of equal length – i.e. they end at the same base position, leaving no unpaired bases on either strand. The concept is used in molecular biology, in cloning, or when subcloning insert DNA into vector DNA. Such ends may be generated by restriction enzymes that break the molecule's phosphodiester backbone at specific locations, which themselves belong to a larger class of enzymes called exonucleases and endonucleases. A restriction enzyme that cuts the backbones of both strands at non-adjacent locations leaves a staggered cut, generating two overlapping sticky ends, while an enzyme that makes a str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G2 Phase
G2 phase, Gap 2 phase, or Growth 2 phase, is the third subphase of interphase in the cell cycle directly preceding mitosis. It follows the successful completion of S phase, during which the cell’s DNA is replicated. G2 phase ends with the onset of prophase, the first phase of mitosis in which the cell’s chromatin condenses into chromosomes. G2 phase is a period of rapid cell growth and protein synthesis during which the cell prepares itself for mitosis. Curiously, G2 phase is not a necessary part of the cell cycle, as some cell types (particularly young ''Xenopus'' embryos and some cancers)) proceed directly from DNA replication to mitosis. Though much is known about the genetic network which regulates G2 phase and subsequent entry into mitosis, there is still much to be discovered concerning its significance and regulation, particularly in regards to cancer. One hypothesis is that the growth in G2 phase is regulated as a method of cell size control. Fission yeast (''Schi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CTBP1
C-terminal-binding protein 1 also known as CtBP1 is a protein that in humans is encoded by the ''CTBP1'' gene. CtBP1 is one of two CtBP proteins, the other protein being CtBP2. Function The CtBP1 protein was originally identified as a human protein that bound a PLDLS motif in the C-terminus of adenovirus E1A proteins. It and the related protein CTBP2 were later shown to function as transcriptional corepressors. That is, regulatory proteins that bind to sequence-specific DNA-binding proteins and help turn genes off. CtBPs do this by recruiting histone modifying enzymes that add repressive histone marks and remove activating marks. CtBP proteins can also self-associate and presumably bring together gene regulatory complexes. CtBP1 is broadly expressed from embryo to adult, while CtBP2 has a somewhat more restricted pattern of expression. CtBPs have multiple biological roles and appear to be most important in regulating the epithelial to mesenchymal transition, as well as influencing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MRX Complex
The MRX complex is a heterotrimeric protein complex consisting of Mre11, Rad50, and Xrs2. It is a budding yeast homolog of the mammalian Mre11-Rad50-Nbs1 (MRN) DNA damage repair complex. Double-strand break repair Cells are able to accurately repair DNA double-strand breaks using a process called homologous recombination. By this process DNA sequence information that is lost because of the breakage can be recovered from a second homologous DNA molecule. Homologous recombinational repair is important for removing DNA damage both during mitosis and meiosis. The repair process begins with the degradation of the 5’ end on either side of the double-strand break to yield 3’ single-stranded DNA tails (a process called end resection). Next the Rad51 protein binds to these tails and initiates a process of strand invasion leading to recovery of genetic information from the undamaged homologous sequence of the second DNA molecule. Studies with the yeast ''Saccharomyces cerevisiae'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nibrin
Nibrin, also known as NBN or NBS1, is a protein which in humans is encoded by the ''NBN'' gene. Function Nibrin is a protein associated with the repair of double strand breaks (DSBs) which pose serious damage to a genome. It is a 754 amino acid protein identified as a member of the NBS1/hMre11/RAD50(N/M/R, more commonly referred to as MRN) double strand DNA break repair complex. This complex recognizes DNA damage and rapidly relocates to DSB sites and forms nuclear foci. It also has a role in regulation of N/M/R (MRN) protein complex activity which includes end-processing of both physiological and mutagenic DNA double strand breaks (DSBs). Cellular response to DSBs Cellular response is performed by damage sensors, effectors of lesion repair and signal transduction. The central role is carried out by ataxia telangiectasia mutated (ATM) by activating the DSB signaling cascade, phosphorylating downstream substrates such as histone H2AX and NBS1. NBS1 relocates to DSB sites ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rad50
DNA repair protein RAD50, also known as RAD50, is a protein that in humans is encoded by the ''RAD50'' gene. Function The protein encoded by this gene is highly similar to ''Saccharomyces cerevisiae'' Rad50, a protein involved in DNA double-strand break repair. This protein forms a complex with MRE11 and NBS1 (also known as Xrs2 in yeast). This MRN complex (MRX complex in yeast) binds to broken DNA ends and displays numerous enzymatic activities that are required for double-strand break repair by nonhomologous end-joining or homologous recombination. Gene knockout studies of the mouse homolog of Rad50 suggest it is essential for cell growth and viability. Two alternatively spliced transcript variants of Rad50, which encode distinct proteins, have been reported. Structure Rad50 is a member of the structural maintenance of chromosomes (SMC) family of proteins. Like other SMC proteins, Rad50 contains a long internal coiled-coil domain that folds back on itself, bringing the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MRE11A
Double-strand break repair protein MRE11 is an enzyme that in humans is encoded by the ''MRE11'' gene. The gene has been designated ''MRE11A'' to distinguish it from the pseudogene ''MRE11B'' that is nowadays named ''MRE11P1''. Function This gene encodes a nuclear protein involved in homologous recombination, telomere length maintenance, and DNA double-strand break repair. By itself, the protein has 3' to 5' exonuclease activity and endonuclease activity. The protein forms a complex with the RAD50 homolog; this complex is required for nonhomologous joining of DNA ends and possesses increased single-stranded DNA endonuclease and 3' to 5' exonuclease activities. In conjunction with a DNA ligase, this protein promotes the joining of noncomplementary ends in vitro using short homologies near the ends of the DNA fragments. This gene has a pseudogene on chromosome 3. Alternative splicing of this gene results in two transcript variants encoding different isoforms. Orthologs Mre11, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protein Complex
A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multienzyme complexes, in which multiple catalytic domains are found in a single polypeptide chain. Protein complexes are a form of quaternary structure. Proteins in a protein complex are linked by non-covalent protein–protein interactions. These complexes are a cornerstone of many (if not most) biological processes. The cell is seen to be composed of modular supramolecular complexes, each of which performs an independent, discrete biological function. Through proximity, the speed and selectivity of binding interactions between enzymatic complex and substrates can be vastly improved, leading to higher cellular efficiency. Many of the techniques used to enter cells and isolate proteins are inherently disruptive to such large complexes, complicating the task of determining the components of a complex. Examples of protein complexes include the p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Conservation
In evolutionary biology, conserved sequences are identical or similar sequences in nucleic acids ( DNA and RNA) or proteins across species ( orthologous sequences), or within a genome ( paralogous sequences), or between donor and receptor taxa ( xenologous sequences). Conservation indicates that a sequence has been maintained by natural selection. A highly conserved sequence is one that has remained relatively unchanged far back up the phylogenetic tree, and hence far back in geological time. Examples of highly conserved sequences include the RNA components of ribosomes present in all domains of life, the homeobox sequences widespread amongst Eukaryotes, and the tmRNA in Bacteria. The study of sequence conservation overlaps with the fields of genomics, proteomics, evolutionary biology, phylogenetics, bioinformatics and mathematics. History The discovery of the role of DNA in heredity, and observations by Frederick Sanger of variation between animal insulins in 1949, prompted ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MRN Complex
The MRN complex (MRX complex in yeast) is a protein complex consisting of Mre11, Rad50 and Nbs1 (also known as Nibrin in humans and as Xrs2 in yeast). In eukaryotes, the MRN/X complex plays an important role in the initial processing of double-strand DNA breaks prior to repair by homologous recombination or non-homologous end joining. The MRN complex binds avidly to double-strand breaks both in vitro and in vivo and may serve to tether broken ends prior to repair by non-homologous end joining or to initiate DNA end resection prior to repair by homologous recombination. The MRN complex also participates in activating the checkpoint kinase ATM in response to DNA damage. Production of short single-strand oligonucleotides by Mre11 endonuclease activity has been implicated in ATM activation by the MRN complex. Evolutionary ancestry and biologic function The MRN complex has been mainly studied in eukaryotes. However, recent work shows that two of the three protein components of this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PARP2
Poly DP-ribosepolymerase 2 is an enzyme that in humans is encoded by the ''PARP2'' gene. It is one of the PARP family of enzymes. Function This gene encodes poly(ADP-ribosyl)transferase-like 2 protein, which contains a catalytic domain and is capable of catalyzing a poly(ADP-ribosyl)ation reaction. This protein has a catalytic domain which is homologous to that of poly (ADP-ribosyl) transferase, but lacks an N-terminal DNA binding domain which activates the C-terminal catalytic domain of poly (ADP-ribosyl) transferase. The basic residues within the N-terminal region of this protein may bear potential DNA-binding properties, and may be involved in the nuclear and/or nucleolar targeting of the protein. Two alternatively spliced transcript variants encoding distinct isoforms have been found. In the plant species Arabidopsis thaliana, PARP2 plays more significant roles than PARP1 in protective responses to DNA damage and bacterial pathogenesis. The plant PARP2 carries N-terminal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). Euka ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
