HMGB1 is a cofactor in mammalian base excision repair.

Deoxyribose phosphate (dRP) removal by DNA polymerase beta (Pol beta) is a pivotal step in base excision repair (BER). To identify BER cofactors, especially those with dRP lyase activity, we used a Pol beta null cell extract and BER intermediate as bait for sodium borohydride crosslinking. Mass spectrometry identified the high-mobility group box 1 protein (HMGB1) as specifically interacting with the BER intermediate.

DNA polymerase lambda protects mouse fibroblasts against oxidative DNA damage and is recruited to sites of DNA damage/repair.

DNA polymerase lambda (pol lambda) is a member of the X family of DNA polymerases that has been implicated in both base excision repair and non-homologous end joining through in vitro studies. However, to date, no phenotype has been associated with cells deficient in this DNA polymerase. Here we show that pol lambda null mouse fibroblasts are hypersensitive to oxidative DNA damaging agents, suggesting a role of pol lambda in protection of cells against the cytotoxic effects of oxidized DNA.

Recombinogenic phenotype of human activation-induced cytosine deaminase.

Class switch recombination, gene conversion, and somatic hypermutation that diversify rearranged Ig genes to produce various classes of high affinity Abs are dependent on the enzyme activation-induced cytosine deaminase (AID). Evidence suggests that somatic hypermutation is due to error-prone DNA repair that is initiated by AID-mediated deamination of cytosine in DNA, whereas the mechanism by which AID controls recombination remains to be elucidated. In this study, using a yeast model system, we have observed AID-dependent recombination.