xpa-mediated regulation of global nucleotide excision repair by atr is p53-dependent and occurs primarily in s-phasexpa-mediated监管全球核苷酸切除修复的atr p53-dependent主要发生在s阶段.pdfVIP

XPA-Mediated Regulation of Global Nucleotide Excision Repair by ATR Is p53-Dependent and Occurs Primarily in S-Phase Zhengke Li, Phillip R. Musich, Moises A. Serrano, Zhiping Dong, Yue Zou* Department of Biochemistry and Molecular Biology, East Tennessee State University, J. H. Quillen College of Medicine, Johnson City, Tennessee, United States of America Abstract Cell cycle checkpoints play an important role in regulation of DNA repair pathways. However, how the regulation occurs throughout the cell cycle remains largely unknown. Here we demonstrate that nucleotide excision repair (NER) is regulated by the ATR/p53 checkpoint via modulation of XPA nuclear import and that this regulation occurs in a cell cycle-dependent manner. We show that depletion of p53 abrogated the UV-induced nuclear translocation of XPA, while silencing of Chk1 or MAPKAP Kinase-2 (MK2) had no effect. Inhibition of p53 transcriptional activities and silencing of p53-Ser15 phosphorylation also reduced the damage-induced XPA nuclear import. Furthermore, in G1-phase cells the majority of XPA remained in the cytoplasm even after UV treatment. By contrast, while most of the XPA in S-phase cells was initially located in the cytoplasm before DNA damage, UV irradiation stimulated bulk import of XPA into the nucleus. Interestingly, the majority of XPA molecules always were located in the nucleus in G2-phase cells no matter whether the DNA was damaged or not. Consistently, the UV-induced Ser15 phosphorylation of p53 occurred mainly in S-phase cells, and removal of cyclobutane pyrimidine dimers (CPDs) was much more efficient in S-phase cells than in G1-phase cells. Our results suggest that upon DNA damage in S phase, NER could be regulated by the ATR/p53-dependent checkpoint via modulation of the XPA nuclear import process. In contrast, the nuclear import of XPA in G1 or G2 phase