Temporal separation of replication and recombination requires the intra-S checkpoint

Abstract

In response to DNA damage and replication pausing, eukaryotes activate checkpoint pathways that prevent genomic instability by coordinating cell cycle progression with DNA repair. The intra-S-phase checkpoint has been proposed to protect stalled replication forks from pathological rearrangements that could result from unscheduled recombination. On the other hand, recombination may be needed to cope with either stalled forks or double-strand breaks resulting from hydroxyurea treatment. We have exploited fission yeast to elucidate the relationship between replication fork stalling, loading of replication and recombination proteins onto DNA, and the intra-S checkpoint. Here, we show that a functional recombination machinery is not essential for recovery from replication fork arrest and instead can lead to nonfunctional fork structures. We find that Rad22-containing foci are rare in S-phase cells, but peak in G2 phase cells after a perturbed S phase. Importantly, we find that the intra-S checkpoint is necessary to avoid aberrant strand-exchange events during a hydroxyurea block.

SUMO-binding Motifs Mediate the Rad60-dependent Response to Replicative Stress and Self-association

“…Uncoupling the interaction between Cds1 and Mus81-Eme1 results in the unscheduled presence of Mus81-Eme1 on chromatin during replication arrest and the subsequent initiation of recombinogenic processes (5). Apparent negative regulation of recombination repair proteins by the replication checkpoint is consistent with the failure to observe recombination repair foci in wild-type fission yeast during hydroxyurea-induced replication arrest (6). Notably, recombination repair foci are observed following release from replication arrest and entry into G 2 phase or during the arrest if Cds1 is deleted (6).…”

“…Apparent negative regulation of recombination repair proteins by the replication checkpoint is consistent with the failure to observe recombination repair foci in wild-type fission yeast during hydroxyurea-induced replication arrest (6). Notably, recombination repair foci are observed following release from replication arrest and entry into G 2 phase or during the arrest if Cds1 is deleted (6).…”

Fission Yeast Hsk1 (Cdc7) Kinase Is Required After Replication Initiation for Induced Mutagenesis and Proper Response to DNA Alkylation Damage

“…To determine whether this reflects active damage, we employed a YFP-tagged Rad22 (ScRad52) to visualize repair foci (Lisby et al 2001(Lisby et al , 2003(Lisby et al , 2004Du et al 2003;Meister et al 2003Meister et al , 2005. We observed that 67.3% of hsk1-1312 cells and 61.6% of Dswi1 cells growing asynchronously at 25°had at least one Rad22YFP focus, vs. only 8.5% of wild-type cells (Figure 2).…”

Schizosaccharomyces pombe Histone Acetyltransferase Mst1 (KAT5) Is an Essential Protein Required for Damage Response and Chromosome Segregation

“…Our data showing an interaction both genetically and physically with Rad22 suggested that Mst1 may contribute to repair of DSBs by influencing homologous recombination. Rad22 has also been implicated in recovery from HU (Meister et al 2005;Bailis et al 2008). Therefore, we examined mst1-L344S mutants for evidence of a role in the damage response.…”