Origin recognition complex (ORC) in transcriptional silencing and DNA replication in S. cerevisiae.
In Saccharomyces cerevisiae, the HMR-E silencer blocks site-specific interactions between proteins and their recognition sequences in the vicinity of the silencer. Silencer function is correlated with the firing of an origin of replication at HMR-E. An essential gene with a role in transcriptional silencing was identified by means of a screen for mutations affecting expression of HMR. This gene, known as ORC2, was shown to encode a component of the origin recognition complex that binds yeast origins of replication. A temperature-sensitive mutation in ORC2 disrupted silencing in cells grown at the permissive temperature. At the restrictive temperature, the orc2-1 mutation caused cell cycle arrest at a point in the cell cycle indicative of blocks in DNA replication. The orc2-1 mutation also resulted in the enhanced mitotic loss of a plasmid, suggestive of a defect in replication. These results provide strong evidence for an in vivo role of ORC in both chromosomal replication and silencing, and provide a link between the mechanism of silencing and DNA replication.
Foss
M
M
Department of Molecular and Cellular Biology, University of California, Berkeley 94720.
McNally
F J
FJ
Laurenson
P
P
Rine
J
J
D000483:Alleles; D000595:Amino Acid Sequence; D002453:Cell Cycle; D003001:Cloning, Molecular; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D051738:Origin Recognition Complex; D010641:Phenotype; D010957:Plasmids; D012093:Replicon; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C497215:ORC2 protein, S cerevisiae; D051738:Origin Recognition Complex; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins