14-3-3 proteins regulate exonuclease 1–dependent processing of stalled replication forks14-3-3蛋白调节核酸外切酶1-dependent处理停滞复制叉.pdfVIP

14-3-3 Proteins Regulate Exonuclease 1–Dependent Processing of Stalled Replication Forks 1 2¤ 2 1 1 Kim Engels , Michele Giannattasio , Marco Muzi-Falconi , Massimo Lopes *, Stefano Ferrari * 1 Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland, 2 Department of Biomolecular Sciences and Biotechnology, University of Milan, Milan, Italy Abstract Replication fork integrity, which is essential for the maintenance of genome stability, is monitored by checkpoint-mediated phosphorylation events. 14-3-3 proteins are able to bind phosphorylated proteins and were shown to play an undefined role under DNA replication stress. Exonuclease 1 (Exo1) processes stalled replication forks in checkpoint-defective yeast cells. We now identify 14-3-3 proteins as in vivo interaction partners of Exo1, both in yeast and mammalian cells. Yeast 14-3- 3–deficient cells fail to induce Mec1–dependent Exo1 hyperphosphorylation and accumulate Exo1–dependent ssDNA gaps at stalled forks, as revealed by electron microscopy. This leads to persistent checkpoint activation and exacerbated recovery defects. Moreover, using DNA bi-dimensional electrophoresis, we show that 14-3-3 proteins promote fork progression under limiting nucleotide concentrations. We propose that 14-3-3 proteins assist in controlling the phosphorylation status of Exo1 and additional unknown targets, promoting fork progression, stability, and restart in response to DNA replication stress. Citation: Engels K, Giannattasio M, Muzi-Falconi M, Lopes M, Ferrari S (2011) 14-3-3 Proteins Regulate Exonuclease 1–Dependent Processing of Stalled Replication Forks. PLoS Genet 7(4): e1001367. doi:10.1371/journal.pgen.1001367 Edit