Sld3, which interacts with Cdc45 (Sld4), functions for chromosomal DNA replication in Saccharomyces cerevisiae.
Cdc45, which binds to the minichromosomal maintenance (Mcm) proteins, has a pivotal role in the initiation and elongation steps of chromosomal DNA replication in eukaryotes. Here we show that throughout the cell cycle in Saccharomyces cerevisiae, Cdc45 forms a complex with a novel factor, Sld3. Consistently, Sld3 and Cdc45 associate simultaneously with replication origins in the chromatin immunoprecipitation assay: both proteins associate with early-firing origins in G(1) phase and with late-firing origins in late S phase. Moreover, the origin associations of Sld3 and Cdc45 are mutually dependent. The temperature-sensitive sld3 mutation confers a defect in DNA replication at the restrictive temperature and reduces an interaction not only between Sld3 and Cdc45, but also between Cdc45 and Mcm2. These results suggest that the Sld3-Cdc45 complex associates with replication origins through Mcm proteins. At the restrictive temperature in sld3-5 cells, replication factor A, a single-strand DNA binding protein, does not associate with origins. Therefore, the origin association of Sld3-Cdc45 complex is prerequisite for origin unwinding in the initiation of DNA replication.
Kamimura
Y
Y
Division of Microbial Genetics, National Institute of Genetics, Osaka University, Osaka 565-0871 Japan.
Tak
Y S
YS
Sugino
A
A
Araki
H
H
D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D015825:Chromosomes, Fungal / Q000378:metabolism*; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D018628:Gene Dosage; D020043:Genes, Essential; D005800:Genes, Fungal; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D018741:Replication Origin; D051716:Replication Protein A; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
C102209:CDC45 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D051716:Replication Protein A; D029701:Saccharomyces cerevisiae Proteins; C426020:Sld3 protein, S cerevisiae