Host: The Japan Radiation Research Society, Chairman of the 52nd Annual Meeting, Toshiteru Okubo (Radiation Effects Research Foundation)
DNA is exposed continuously to various exogenous or endogenous damaging factors. Most of simple altered bases emerged under the physiological condition are repaired by base excision repair (BER). BER is initiated by removal of the altered base by specific DNA glycosylase leaving apurinic/apyrimidinic site (AP site). This process leads to two repair pathways, short-patch BER (SP-BER) and long-patch BER (LP-BER) in which polymerase β (polβ) and Flap endonuclease 1 (Fen1) take major roles, respectively. We constructed the RNAi inductive plasmid that using the shRNA expression vector to clarify how SP-BER and LP-BER were selected for the repair of alkylated base damages. By introducing the plasmid into mouse embryonic fibroblast (MEF), the knockdown (KD) cells were obtained. The KD efficiency was 87% in polβ, and 92% in Fen1 KD cells when the protein levels were examined by western blotting analysis. Despite the almost same suppression levels, the polβ KD cell showed significantly higher sensitivity to methylmethanesulfonate than the Fen1 KD cell. Detailed kinetic study is in progress to reveal the relative contribution of two BER subpathways to the repair of MMS damages.
