Regulation of replication protein A functions in DNA mismatch repair by phosphorylation.
Replication protein A (RPA) is involved in multiple stages of DNA mismatch repair (MMR); however, the modulation of its functions between different stages is unknown. We show here that phosphorylation likely modulates RPA functions during MMR. Unphosphorylated RPA initially binds to nicked heteroduplex DNA to facilitate assembly of the MMR initiation complex. The unphosphorylated protein preferentially stimulates mismatch-provoked excision, possibly by cooperatively binding to the resultant single-stranded DNA gap. The DNA-bound RPA begins to be phosphorylated after extensive excision, resulting in severalfold reduction in the DNA binding affinity of RPA. Thus, during the phase of repair DNA synthesis, the phosphorylated RPA readily disassociates from DNA, making the DNA template available for DNA polymerase delta-catalyzed resynthesis. These observations support a model of how phosphorylation alters the DNA binding affinity of RPA to fulfill its differential requirement at the various stages of MMR.
Guo
Shuangli
S
Department of Molecular & Cellular Biochemistry and Markey Cancer Center, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Zhang
Yanbin
Y
Graduate Center for Toxicology and Department of Pathology, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Yuan
Fenghua
F
Graduate Center for Toxicology and Department of Pathology, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Gao
Yin
Y
Graduate Center for Toxicology and Department of Pathology, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Gu
Liya
L
Graduate Center for Toxicology and Department of Pathology, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Wong
Isaac
I
Department of Molecular & Cellular Biochemistry and Markey Cancer Center, University of Kentucky Medical Center, Lexington, Kentucky 40536.
Li
Guo-Min
GM
Department of Molecular & Cellular Biochemistry and Markey Cancer Center, University of Kentucky Medical Center, Lexington, Kentucky 40536; Graduate Center for Toxicology and Department of Pathology, University of Kentucky Medical Center, Lexington, Kentucky 40536. Electronic address: gmli@uky.edu.
D020137:Base Pair Mismatch / Q000235:genetics*; D004258:DNA Polymerase III / Q000378:metabolism; D004260:DNA Repair; D004270:DNA, Circular / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D051716:Replication Protein A / Q000378:metabolism* / Q000502:physiology*; D013698:Templates, Genetic
D004270:DNA, Circular; D051716:Replication Protein A; D004258:DNA Polymerase III