Watching a double strand break repair polymerase insert a pro-mutagenic oxidized nucleotide

Oxidized dGTP (8-oxo-7,8-dihydro-2-deoxyguanosine triphosphate, 8-oxodGTP) insertion by DNA polymerases strongly promotes cancer and human disease. How DNA polymerases discriminate against oxidized and undamaged nucleotides, especially in error-prone double strand break (DSB) repair, is poorly understood. High-resolution time-lapse X-ray crystallography snapshots of DSB repair polymerase mu undergoing DNA synthesis reveal that a third active site metal promotes insertion of oxidized and undamaged dGTP in the canonical anti-conformation opposite template cytosine. The product metal bridged O8 with product oxygens, and was not observed in the syn-conformation opposite template adenine (A(t)). Rotation of A(t) into the syn-conformation enabled undamaged dGTP misinsertion. Exploiting metal and substrate dynamics in a rigid active site allows 8-oxodGTP to circumvent polymerase fidelity safeguards to promote pro-mutagenic double strand break repair. How DNA polymerases discriminate against oxidized and undamaged nucleotides during DNA repair is not fully understood. Here, the authors reveal high-resolution timelapse X-ray crystallography snapshots of DSB repair polymerase mu undergoing DNA synthesis providing mechanistic insights into the process.

Automated summary

The study demonstrates how DNA polymerases discriminate against oxidized and undamaged nucleotides during error-prone double strand break repair, through high-resolution time-lapse X-ray crystallography snapshots of DSB repair polymerase mu undergoing DNA synthesis.