Identification of Tah11/Sid2 as the ortholog of the replication licensing factor Cdt1 in Saccharomyces cerevisiae.
Faithful duplication of the genetic material requires that replication origins fire only once per cell cycle. Central to this control is the tightly regulated formation of prereplicative complexes (preRCs) at future origins of DNA replication. In all eukaryotes studied, this entails loading by Cdc6 of the Mcm2-7 helicase next to the origin recognition complex (ORC). More recently, another factor, named Cdt1, was shown to be essential for Mcm loading in fission yeast and Xenopus as well as for DNA replication in Drosophila and humans. Surprisingly, no Cdt1 homolog was found in budding yeast, despite the conserved nature of origin licensing. Here we identify Tah11/Sid2, previously isolated through interactions with topoisomerase and Cdk inhibitor mutants, as an ortholog of Cdt1. We show that sid2 mutants lose minichromosomes in an ARS number-dependent manner, consistent with ScCdt1/Sid2 being involved in origin licensing. Accordingly, cells partially depleted of Cdt1 replicate DNA from fewer origins, whereas fully depleted cells fail to load Mcm2 on chromatin and fail to initiate but not elongate DNA synthesis. We conclude that origin licensing depends in S. cerevisiae as in other eukaryotes on both Cdc6 and Cdt1.
Devault
Alain
A
Institute of Molecular Genetics, CNRS UMR 5535 and Université Montpellier II, 1919, Route de Mende, 34293 cedex 5, Montpellier, France.
Vallen
Elizabeth A
EA
Yuan
Tina
T
Green
Stephen
S
Bensimon
Aaron
A
Schwob
Etienne
E
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry*; D002843:Chromatin / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry*; D005656:Fungal Proteins / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D011494:Protein Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018741:Replication Origin / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
C467199:CDT1 protein, human; D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; C499592:TAH11 protein, S cerevisiae; D011494:Protein Kinases; C069199:MCM2 protein, S cerevisiae