Dual Modes of Interaction between XRCC4 and Polynucleotide Kinase/Phosphatase: IMPLICATIONS FOR NONHOMOLOGOUS END JOINING

• Published in: The Journal of biological chemistry Vol. 285; no. 48; pp. 37619 - 37629
• Main Authors: Mani, Rajam S, Yu, Yaping, Fang, Shujuan, Lu, Meiling, Fanta, Mesfin, Zolner, Angela E, Tahbaz, Nasser, Ramsden, Dale A, Litchfield, David W, Lees-Miller, Susan P, Weinfeld, Michael
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 26.11.2010
• Subjects: Casein Kinase II - genetics; Casein Kinase II - metabolism; DNA - genetics; DNA - metabolism; DNA Ligases - genetics; DNA Ligases - metabolism; DNA Repair; DNA Repair Enzymes - genetics; DNA Repair Enzymes - metabolism; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Enzymology; HeLa Cells; Humans; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor) - genetics; Phosphotransferases (Alcohol Group Acceptor) - metabolism; Protein Binding; Protein Structure, Tertiary
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M109.058719

XRCC4 plays a crucial role in the nonhomologous end joining (NHEJ) pathway of DNA double-strand break repair acting as a scaffold protein that recruits other NHEJ proteins to double-strand breaks. Phosphorylation of XRCC4 by protein kinase CK2 promotes a high affinity interaction with the forkhead-associated domain of the end-processing enzyme polynucleotide kinase/phosphatase (PNKP). Here we reveal that unphosphorylated XRCC4 also interacts with PNKP through a lower affinity interaction site within the catalytic domain and that this interaction stimulates the turnover of PNKP. Unexpectedly, CK2-phosphorylated XRCC4 inhibited PNKP activity. Moreover, the XRCC4·DNA ligase IV complex also stimulated PNKP enzyme turnover, and this effect was independent of the phosphorylation of XRCC4 at threonine 233. Our results reveal that CK2-mediated phosphorylation of XRCC4 can have different effects on PNKP activity, with implications for the roles of XRCC4 and PNKP in NHEJ.