%0 Journal Article
%T Critical Function of ¦ÃH2A in S-Phase
%A Eva Mejia-Ramirez&nbsp
%A Oliver Limbo&nbsp
%A Petra Langerak&nbsp
%A Paul Russell
%J PLOS Genetics
%D 2015
%I Public Library of Science (PLoS)
%R 10.1371/journal.pgen.1005517
%X Phosphorylation of histone H2AX by ATM and ATR establishes a chromatin recruitment platform for DNA damage response proteins. Phospho-H2AX (¦ÃH2AX) has been most intensively studied in the context of DNA double-strand breaks caused by exogenous clastogens, but recent studies suggest that DNA replication stress also triggers formation of ¦ÃH2A (ortholog of ¦ÃH2AX) in Schizosaccharomyces pombe. Here, a focused genetic screen in fission yeast reveals that ¦ÃH2A is critical when there are defects in Replication Factor C (RFC), which loads proliferating cell nuclear antigen (PCNA) clamp onto duplex DNA. Surprisingly Chk1, Cds1/Chk2 and the Rad9-Hus1-Rad1 checkpoint clamp, which are crucial for surviving many genotoxins, are fully dispensable in RFC-defective cells. Immunoblot analysis confirms that Rad9-Hus1-Rad1 is not required for formation of ¦ÃH2A by Rad3/ATR in S-phase. Defects in DNA polymerase epsilon, which binds PCNA in the replisome, also create an acute need for ¦ÃH2A. These requirements for ¦ÃH2A were traced to its role in docking with Brc1, which is a 6-BRCT-domain protein that is structurally related to budding yeast Rtt107 and mammalian PTIP. Brc1, which localizes at stalled replication forks by binding ¦ÃH2A, prevents aberrant formation of Replication Protein A (RPA) foci in RFC-impaired cells, suggesting that Brc1-coated chromatin stabilizes replisomes when PCNA or DNA polymerase availability limits DNA synthesis.
%U http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1005517