STUDY ON NOVEL REQULATORY MECHANISMA OF DNA REPAIR

点击翻译按钮获取中文摘要

In order to investigate how DNA repair systems are regulated, we analysed molecular mechanisms of nucleotide excision repair (NER) and translesion synthesis (TLS) in eukaryotic cells, and obtained the following results.1) The XPC-HR23B protein complex, the initiator of global genome NER, was found to associate with a centrosome protein centrin 2.2) The XPC-HR23B strongly recognized specific secondary structures of DNA, involving a single-and double-strand junction. A DNase I footprint analysis, using a looped DNA substrate, revealed that a single XPC-HR23B complex protected a distorted site in an asymmetrical manner.3) While mHR23A KO mice showed no abnormalities, mHR23B KO mice showed impaired embryonic development and a high rate of intrauterine or neonatal death. Surviving animals display a variety of abnormalities, including retarded growth, facial dysmorphology, and male sterility.4) XPC was found to interact with thymine DNA glycosylase (TDG) in yeast two hybrid screening. By biochemical analyses, XPC interacted with TDG not only physically but also functionally.5) We identified two fission yeast homologs of budding yeast Rad4 and human XPC, designated Rfp4A and Rhp4B. Rhp4A was found to play roles in GGR and TCR, while Rhp4B acts as an accessory protein in GGR.6) Human DNA polymerase η (Pol η) catalyzed relatively efficient and accurate TLS past 5R-thymineglycol and 5S-thymineglycol.7) Both alleles of DNA polymerase τ (Pol τ) gene was found to have null mutation in 129-derived strains of mice. Overall frequency and spectrum of mutation were normal in Pol τ-deficient mice.