DNA-POLYMERASE-ALPHA AND DNA-POLYMERASE-BETA ARE REQUIRED FOR DNA-REPAIR IN AN EFFICIENT NUCLEAR EXTRACT FROM XENOPUS OOCYTES

Xenopus oocytes and an oocyte nuclear extract efficiently repair the b ulky DNA lesions cyclobutane pyrimidine dimers, (6-4) photoproducts, a nd N-acetoxy-2-aminofluorene (AAF) adducts by san excision repair mech anism. Nearly all (>95%) of the input damaged DNA was repaired within 5 h in both infected cells and extracts with no significant incorporat ion of label into control undamaged DNA. Remarkably, more than 10(10) cyclobutane pyrimidine dimers or (6-4) photoproducts are repaired/nucl ei. The extracts are free from nuclease activity, and repair is indepe ndent of exogenous light. Both the high efficiency and DNA polymerase requirements of this system appear to be different from extracts deriv ed from human cells. We demonstrated a requirement for DNA polymerases alpha and beta in repair of both photoproducts and AAF by inhibiting repair with several independent antibodies specific to either DNA poly merases alpha or beta and then restoring repair by adding the appropri ate purified polymerase. Repair is inhibited by aphidicolin at concent rations specific for blocking DNA polymerase alpha and dideoxynucleoti de triphosphates at concentrations specific for inhibiting DNA polymer ase beta.