Polymerase (DNA directed) nu is a protein in humans that is encoded by the POLN gene. [3] It is a family A DNA polymerase, [4] considered to be the least effective of the polymerase enzymes. [5] However, DNA polymerase nu plays an active role in homology repair during cellular responses to crosslinks, fulfilling its role in a complex with helicase. [5]
A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to create two identical DNA duplexes from a single original DNA duplex. During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. These enzymes catalyze the chemical reaction
DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day. Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes. Other lesions induce potentially harmful mutations in the cell's genome, which affect the survival of its daughter cells after it undergoes mitosis. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. When normal repair processes fail, and when cellular apoptosis does not occur, irreparable DNA damage may occur, including double-strand breaks and DNA crosslinkages. This can eventually lead to malignant tumors, or cancer as per the two hit hypothesis.
RNA polymerase II is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of eukaryotic cells. A 550 kDa complex of 12 subunits, RNAP II is the most studied type of RNA polymerase. A wide range of transcription factors are required for it to bind to upstream gene promoters and begin transcription.
In genetics, crosslinking of DNA occurs when various exogenous or endogenous agents react with two nucleotides of DNA, forming a covalent linkage between them. This crosslink can occur within the same strand (intrastrand) or between opposite strands of double-stranded DNA (interstrand). These adducts interfere with cellular metabolism, such as DNA replication and transcription, triggering cell death. These crosslinks can, however, be repaired through excision or recombination pathways.
Richard D. Wood is an American molecular biologist specializing in research on DNA repair and mutation. He is known for pioneering studies on nucleotide excision repair (NER), particularly for reconstituting the minimum set of proteins involved in this process, identifying proliferating cell nuclear antigen (PCNA) as part of the NER complex and identifying mammalian repair polymerases.
DNA repair protein XRCC1, also known as X-ray repair cross-complementing protein 1, is a protein that in humans is encoded by the XRCC1 gene. XRCC1 is involved in DNA repair, where it complexes with DNA ligase III.
Poly [ADP-ribose] polymerase 1 (PARP-1) also known as NAD+ ADP-ribosyltransferase 1 or poly[ADP-ribose] synthase 1 is an enzyme that in humans is encoded by the PARP1 gene. It is the most abundant of the PARP family of enzymes, accounting for 90% of the NAD+ used by the family.
Replication protein A 70 kDa DNA-binding subunit is a protein that in humans is encoded by the RPA1 gene.
DNA polymerase beta, also known as POLB, is an enzyme present in eukaryotes. In humans, it is encoded by the POLB gene.
DNA repair protein complementing XP-G cells is a protein that in humans is encoded by the ERCC5 gene.
DNA polymerase lambda, also known as Pol λ, is an enzyme found in all eukaryotes. In humans, it is encoded by the POLL gene.
The gene polymerase delta 1 (POLD1) encodes the large, POLD1/p125, catalytic subunit of the DNA polymerase delta (Polδ) complex. The Polδ enzyme is responsible for synthesizing the lagging strand of DNA, and has also been implicated in some activities at the leading strand. The POLD1/p125 subunit encodes both DNA polymerizing and exonuclease domains, which provide the protein an important second function in proofreading to ensure replication accuracy during DNA synthesis, and in a number of types of replication-linked DNA repair following DNA damage. Germline mutations impairing activity of POLD1 have been implicated in several types of hereditary cancer, in some sporadic cancers, and in a developmental syndrome of premature aging, Mandibular hypoplasia, Deafness, and Progeroid features and Lipodystrophy. Studies of POLD1 emphasize the importance of maintaining genomic stability to limit tumorigenesis. It is currently unclear whether the enhanced tumorigenesis associated with POLD1 defects is the result of increased base substitutions or due to fork collapse and production of DNA double strand breaks (DSBs). Recent reviews have addressed important functions of POLD1 and Polδ.
DNA polymerase theta is an enzyme that in humans is encoded by the POLQ gene. This polymerase plays a key role in one of the three major double strand break repair pathways: theta-mediated end joining. Most double-strand breaks are repaired by non-homologous end joining (NHEJ) or homology directed repair (HDR). However, in some contexts, NHEJ and HR are insufficient and TMEJ is the only solution to repair the break. TMEJ is often described as alternative NHEJ, but differs in that it lacks a requirement for the Ku heterodimer, and it can only act on resected DNA ends. Following annealing of short regions on the DNA overhangs, DNA polymerase theta catalyzes template-dependent DNA synthesis across the broken ends, stabilizing the paired structure.
Zinc finger protein 143 is a protein that in humans is encoded by the ZNF143 gene.
DNA polymerase eta, is a protein that in humans is encoded by the POLH gene.
Alternative Lengthening of Telomeres is a telomerase-independent mechanism by which cancer cells avoid the degradation of telomeres.
DNA ligase 3 is an enzyme that, in humans, is encoded by the LIG3 gene. The human LIG3 gene encodes ATP-dependent DNA ligases that seal interruptions in the phosphodiester backbone of duplex DNA.
DNA polymerase epsilon is a member of the DNA polymerase family of enzymes found in eukaryotes. It is composed of the following four subunits: POLE, POLE2, POLE3, and POLE4. Recent evidence suggests that it plays a major role in leading strand DNA synthesis and nucleotide and base excision repair.
DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the POLA1 gene.
Helicase, POLQ-like, also known as hel308 and Holliday junction migration protein, encoded by the gene HEL308, is a DNA helicase found in humans, archea and many other organisms. Its principal function is to allow DNA replication to continue past DNA forks.
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