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Diagram of both the TC-NER and GG-NER pathways. The two pathways differ only in initial DNA damage recognition. [1] Nucleotide excision repair is a DNA repair mechanism. [2] DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens.
A DNA polymerase is a member of a family of ... Unlike other DNA polymerases, the structure and mechanism of the DP2 ... a DNA repair pathway that is essential for ...
DNA polymerase theta is an enzyme that in humans is encoded by the POLQ gene. [ 5 ] [ 6 ] This polymerase plays a key role in one of the three major double strand break repair pathways: theta-mediated end joining (TMEJ).
Upon activation by the MutS-DNA complex, MutH nicks the daughter strand near the hemimethylated site. MutL recruits UvrD helicase (DNA Helicase II) to separate the two strands with a specific 3' to 5' polarity. The entire MutSHL complex then slides along the DNA in the direction of the mismatch, liberating the strand to be excised as it goes.
PARP1 acts as a first responder that detects DNA damage and then facilitates choice of repair pathway. [12] PARP1 contributes to repair efficiency by ADP-ribosylation of histones leading to decompaction of chromatin structure, and by interacting with and modifying multiple DNA repair factors. [6]
The crystal structure of pol λ shows that, unlike the DNA polymerases that catalyze DNA replication, pol λ makes extensive contacts with the 5' phosphate of the downstream DNA strand. This allows the polymerase to stabilize the two ends of a double-strand break and explains how pol λ is uniquely suited for a role in non-homologous end joining.
Pol β is the main human polymerase that catalyzes short-patch BER, with pol λ able to compensate in its absence. [8] These polymerases are members of the Pol X family and typically insert only a single nucleotide. In addition to polymerase activity, these enzymes have a lyase domain that removes the 5' dRP left behind by AP endonuclease cleavage.
Poly (ADP-ribose) polymerase (PARP) is a family of proteins involved in a number of cellular processes such as DNA repair, genomic stability, and programmed cell death. [ 1 ] Members of PARP family