A conserved Pol? binding module in Ctf18-RFC is required for S-phase checkpoint activation downstream of Mec1.

ABSTRACT: Defects during chromosome replication in eukaryotes activate a signaling pathway called the S-phase checkpoint, which produces a multifaceted response that preserves genome integrity at stalled DNA replication forks. Work with budding yeast showed that the 'alternative clamp loader' known as Ctf18-RFC acts by an unknown mechanism to activate the checkpoint kinase Rad53, which then mediates much of the checkpoint response. Here we show that budding yeast Ctf18-RFC associates with DNA polymerase epsilon, via an evolutionarily conserved 'Pol ? binding module' in Ctf18-RFC that is produced by interaction of the carboxyl terminus of Ctf18 with the Ctf8 and Dcc1 subunits. Mutations at the end of Ctf18 disrupt the integrity of the Pol ? binding module and block the S-phase checkpoint pathway, downstream of the Mec1 kinase that is the budding yeast orthologue of mammalian ATR. Similar defects in checkpoint activation are produced by mutations that displace Pol ? from the replisome. These findings indicate that the association of Ctf18-RFC with Pol ? at defective replication forks is a key step in activation of the S-phase checkpoint.

SUBMITTER: Garcia-Rodriguez LJ 

PROVIDER: S-EPMC4605302 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature