Mismatch repair, BER/NER, double-strand-break repair (HR, NHEJ), homologous recombination.
Dna Repair And Recombination
DNA damage
Endogenous (hydrolysis, oxidation, alkylation, replication errors) or exogenous (UV, ionising radiation, chemical mutagens) lesions.…
Mismatch repair (MMR)
Post-replicative correction of base-base mismatches and small indels. MutSα/β recognise lesion; MutLα nicks daughter strand; EXO1 excises;…
Base excision repair (BER)
Lesion-specific DNA glycosylase removes damaged base (8-oxo-G, uracil, alkylated base) creating AP site → AP endonuclease → gap-fill by Pol…
Nucleotide excision repair (NER)
Repairs bulky/helix-distorting lesions (UV pyrimidine dimers, chemical adducts). XPC or CSB recognises, TFIIH unwinds, XPF/XPG excise…
Homologous recombination (HR)
Error-free double-strand break repair using sister chromatid as template. End resection by MRN + CtIP → RAD51 filament → strand invasion →…
Non-homologous end joining (NHEJ)
Error-prone DSB repair via direct ligation of broken ends. Ku70/80 + DNA-PKcs + Artemis + XRCC4/LigIV. Active throughout cell cycle;…
DNA double-strand break (DSB)
Most cytotoxic DNA lesion: both strands severed. Sensed by MRN complex; γH2AX phosphorylation marks chromatin. Repaired by HR (S/G2) or…
Direct reversal repair
Single-enzyme reversal of specific lesions: photolyase reverses pyrimidine dimers; MGMT removes O6-methylguanine alkyl groups. No excision…
Translesion DNA synthesis
Y-family polymerases (Polη, Polκ, Polι, Rev1) bypass bulky lesions during replication at cost of accuracy. Essential for UV damage…
BRCA/Fanconi anemia pathway
BRCA1/BRCA2 + FA core complex coordinate HR repair of interstrand crosslinks. Germline mutations predispose to breast/ovarian cancer;…