Abstract
Tumor suppressor p53 is an essential component to maintain the genomic integrity in mammalian cells. Loss p53 compromises the capacity of nucleotide excision repair (NER). Our previous study has shown that p53 is essential to nuclear extracts to excise UVC-induced DNA lesions in comet-NE assay, and the positions 299-308 (LPPGSTKRAL) of p53 is indispensable to both the excision activity and the p53: XPB interaction. In this study, the two positive charged amino acid residues, K305 and R306 of positions 299-308 were substituted with alanine, individually or simultaneously, to test the importance of electrostatic contribution in this regard. Results of the study show that the excision activity of nuclear extract and the recruitment of XPB and RPA to UV-induced DNA damage sites was reduced in the order of K305A≧ R306A/K305A> R306A. RPA is a single- DNA binding protein, it is recruited to the DNA damage sites during NER pathway once the duplex DNA of the sites are unwound by helicase XPB/XPD of TFIIH complex. This study demonstrates the importance of electrostatic contribution to p53: XPB interaction in NER.