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Vol. 19, Issue 2, 595-607, February 2008
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*Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102; and
Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, IL 60607
Submitted June 28, 2007;
Revised November 9, 2007;
Accepted November 19, 2007
Monitoring Editor: Mark Solomon
Sister chromatid cohesion is established during S phase near the replication fork. However, how DNA replication is coordinated with chromosomal cohesion pathway is largely unknown. Here, we report studies of fission yeast Ctf18, a subunit of the RFCCtf18 replication factor C complex, and Chl1, a putative DNA helicase. We show that RFCCtf18 is essential in the absence of the Swi1–Swi3 replication fork protection complex required for the S phase stress response. Loss of Ctf18 leads to an increased sensitivity to S phase stressing agents, a decreased level of Cds1 kinase activity, and accumulation of DNA damage during S phase. Ctf18 associates with chromatin during S phase, and it is required for the proper resumption of replication after fork arrest. We also show that chl1
is synthetically lethal with ctf18
and that a dosage increase of chl1+ rescues sensitivities of swi1
to S phase stressing agents, indicating that Chl1 is involved in the S phase stress response. Finally, we demonstrate that inactivation of Ctf18, Chl1, or Swi1-Swi3 leads to defective centromere cohesion, suggesting the role of these proteins in chromosome segregation. We propose that RFCCtf18 and the Swi1–Swi3 complex function in separate and redundant pathways essential for replication fork stabilization to facilitate sister chromatid cohesion in fission yeast.
Address correspondence to: Eishi Noguchi (enoguchi{at}drexelmed.edu)
Abbreviations used: CPT, camptothecin; FPC, fork protection complex; HU, hydroxyurea; MMS, methylmethane sulfonate; PCNA, proliferating cell nuclear antigen; PFGE, Pulsed field gel electrophoresis; RFC, replication factor C; TBZ, thiabendazole.