Biophysical and structural study on the interaction of Srs2 with PCNA

Abstract

Proliferating cell nuclear antigen (PCNA) is a homo-trimeric DNA-encircling protein that functions as a polymerase processivity factor and also regulator in DNA metabolism. Post translational modification (PTM) on PCNA by Small-ubiquitin-modifier (SUMO) contributes to suppression of hyper-homologous recombination by binding DNA helicase, Srs2. Srs2 is known as DNA helicase that inhibits recombination as it disrupts Rad51 nucleoprotein filaments, functionally cooperates with PCNA and it shows preference for interacting directly with the SUMO-modified form of PCNA. However, the mechanism of interaction between Srs2 and PCNA, and between Srs2 and SUMO remains unclear. Here we show by Nuclear magnetic resonance (NMR) and biophysical analysis that PCNA directly binds with C terminal of Srs2. Our findings suggest a model in which PCNA recruits Srs2 in anti-recombinogetic role of Srs2.