Fission Yeast Cdc24 Is a Replication Factor C- and Proliferating Cell Nuclear Antigen-Interacting Factor Essential for S-Phase Completion

Abstract

At the nonpermissive temperature the fission yeast cdc24-M38 mutant arrests in the cell cycle with incomplete DNA replication as indicated by pulsed-field gel electrophoresis. The cdc24 ؉ gene encodes a 501-aminoacid protein with no significant homology to any known proteins. The temperature-sensitive cdc24 mutant is effectively rescued by pcn1 ؉ , rfc1 ؉ (a fission yeast homologue of RFC1), and hhp1 ؉ , which encode the proliferating cell nuclear antigen (PCNA), the large subunit of replication factor C (RFC), and a casein kinase I involved in DNA damage repair, respectively. The Cdc24 protein binds PCNA and RFC1 in vivo, and the domains essential for Cdc24 function and for RFC1 and PCNA binding colocalize in the N-terminal two-thirds of the molecule. In addition, cdc24؉ genetically interacts with the gene encoding the catalytic subunit of DNA polymerase , which is stimulated by PCNA and RFC, and with those encoding the fission yeast counterparts of Mcm2, Mcm4, and Mcm10. These results indicate that Cdc24 is an RFC-and PCNA-interacting factor required for DNA replication and might serve as a target for regulation.Chromosomal DNA is replicated by cooperation of a number of factors and enzymes. In the budding yeast Saccharomyces cerevisiae they include the origin recognition complex, which is composed of the six subunits called Orc1 to Orc6 (4); Cdc6 (8); minichromosome maintenance (MCM) proteins (56); and at least three DNA polymerases. The origin recognition complex recognizes and binds origins of replication throughout the cell cycle. When cells enter S phase, MCM proteins are loaded onto the origins in a Cdc6-dependent manner (2, 53), and finally DNA polymerase ␣ (Pol ␣), Pol ␦, and Pol ε are recruited to start DNA synthesis. A recent analysis indicates that not only these polymerases but also some MCM proteins are components of replication forks (2).The roles of Pol ␣, Pol ␦, and other factors in DNA replication were initially elucidated by studies with a cell-free simian virus 40 (SV40) DNA replication system (reviewed in references 51 and 58). In this system, Pol ␣ with its primase subunits synthesizes RNA primers and elongates them to short initiator DNAs, which in turn serve as primers for the leadingand lagging-strand synthesis that is catalyzed by Pol ␦. Thus, during DNA replication, the polymerase used for synthesis is switched from ␣ to ␦. This switch requires two accessory proteins, replication factor C (RFC) and proliferating cell nuclear antigen (PCNA) (55). RFC binds the primer ends and thereby recruits and loads PCNA onto them (29, 54). Subsequently, Pol ␦ binds the complex and elongates the DNA strands with high processivity (54). RFC is composed of five related subunits, one large and four small ones. By contrast, PCNA forms homotrimers to act as a sliding clamp (27). This factor is essential for the high processivity of Pol ␦ (47, 48). These polymerases and accessory proteins are highly conserved throughout eukaryotes. The replication of chromosomal DNA, however, requires another type of DNA ...

DNA replication meets genetic exchange: Chromosomal damage and its repair by homologous recombination

“…dna2 ϩ was also isolated as a multicopy suppressor of a cdc24 mutant in S. pombe (88); cdc24 mutants arrest after completing chromosome replication with signs of chromosome fragmentation (88). In addition to dna2 ϩ , cdc24 mutants are also rescued by multiple copies of pcn1 ϩ (DNA clamp) and rfc1 ϩ (DNA clamp loader) genes; Cdc24p binds to Pcn1p and Rfc1p in vivo (89). A defect in Okazaki fragment maturation is suspected to lead to the phenotypes of cdc24 mutants.…”

Saccharomyces cerevisiaeCTF18 and CTF4 Are Required for Sister Chromatid Cohesion

“…8C) of a multiple alignment containing the Ctf18p homologs and Rfc1 proteins from S. cerevisiae, C. elegans, D. melanogaster, S. pombe, and H. sapiens. The Rfc1 proteins have been experimentally defined (71,98) with the exception of the C. elegans predicted Rfc1p. In cluster analysis, the Ctf18p homologs form a group apart from the Rfc1 proteins.…”

Primer Utilization by DNA Polymerase α-Primase Is Influenced by Its Interaction with Mcm10p

“…Mutations in MCM10 result in a delay in the completion of DNA synthesis after cells are released from HU arrest (23), suggesting that Mcm10p is essential for continued fork progression. MCM10 mutants are suppressed by mutant MCM5 and MCM7 genes and are synthetically lethal with mutant genes of ORC, CDC45, DNA2, DPB11, and genes encoding subunits of DNA polymerase ␦ and ⑀ (22)(23)(24)(25)(26)(27). Seven new mutants named slm1-slm6 for synthetically lethal with mcm10 include mutations in genes that are allelic to MCM7, MCM2, CDC45, DNA2, and mutations in novel DNA repair genes represented by SLM2 and SLM6 (28).…”