Authors:
Xuan Li, Carrie M. Stith, Peter M. Burgers, and Wolf-Dietrich Heyer
Summary:
Genetic recombination ensures proper chromosome segregation during meiosis and is essential for genome stability and tumor suppression. DNA synthesis after Rad51-mediated DNA strand invasion is a crucial step during recombination. PCNA is known as the processivity clamp for DNA polymerases. Here, we report the surprising observation that PCNA is specifically required to initiate recombination-associated DNA synthesis in the extension of the 3' end of the invading strand in a D loop. We show using a reconstituted system of yeast Rad51, Rad54, RPA, PCNA, RFC, and DNA polymerase δ that loading of PCNA by RFC targets DNA polymerase δ to the D loop formed by Rad51 protein, allowing efficient utilization of the invading 3' end and processive DNA synthesis. We conclude that PCNA has a specific role in the initiation of recombination-associated DNA synthesis and that DNA polymerase δ promotes recombination-associated DNA synthesis.
Source:
Molecular Cell; Vol. 36, Issue 4, 704-713 (11/25/09)