Molecular Analysis of Human DNA Excision Repair Mechanism.

点击翻译按钮获取中文摘要

Kiyoji Tanaka, a head investigator, and Yoshimichi Nakatsu and Masafumi Saijo, collaborative investigators, have visited Jan H.J.Hoeijmakers at Erasmus University Rotterdam and discussed on the analyzes of DNA repair functions of xeroderma pigmentosum group A(XPA)and ERCC1 genes.Tanaka and Saijo found that the XPA protein is a zinc metalloprotein consisting of 273 amino acids which binds preferentially to UV-or chemical carcinogen-damaged DNA,and identified a DNA binding domain of the XPA protein which is contained within a truncated derivative of the XPA protein, MF122, consisting of 122 amino acids and containing a C4 type zinc finger motif.These results suggest that the N-terminal and C-terminal regions of the XPA protein may have an important DNA repair function other than DNA binding.We speculated that they might be domains for a protein-protein interaction to cordinate the DNA excision repair processes, and therefore we searched for proteins which interact with the XPA protein us … More ing yeast two hybrid system.We found that the RPA(replication protein A)and ERCC1 proteins interact with the XPA protein.The interaction between ERCC1 and XPA proteins was confirmed in in vitro assay by the collaboration with Hoeijmakers, and a domain of the XPA protein to interact with the ERCC1 protein was assigned to the N-terminal region containing E-cluster region.Tanaka also found that the interaction of the XPA and ERCC1 proteins caused an enhancement of the damaged DNA binding activity of the XPA protein.It has been suggested that the XPA protein may play a role in loading the incision complex onto a damaged DNA site by the interaction with ERCC1 protein.In addition, our results indicate that the interaction is also to increase the affinity of the repair protein complex for the damaged DNA.Tanaka has established the XPA deficient mice by gene targeting in ES cells.The homozygotes were fertile and showed no obvious physical abnormalities, but they were defective in the DNA excision repair.When they were treated with DMBA or irradiated with UVB,they developed papillomas and squamous cell carcinomas at higher frequency than wild type mice.Hoeijmaker has developed the ERCC1 deficient mice which were runted at birth and died before weaning, suggesting that the ERCC1 gene is indispensable for normal development.Thus the XPA-deficient mice provides a useful model to study UV-or chemical carcinogenesis and mutagenesis in vivo. Less