DNA replication-independent silencing in S. cerevisiae.
In Saccharomyces cerevisiae, the silent mating loci are repressed by their assembly into heterochromatin. The formation of this heterochromatin requires a cell cycle event that occurs between early S phase and G(2)/M phase, which has been widely assumed to be DNA replication. To determine whether DNA replication through a silent mating-type locus, HMRa, is required for silencing to be established, we monitored heterochromatin formation at HMRa on a chromosome and on a nonreplicating extrachromosomal cassette as cells passed through S phase. Cells that passed through S phase established silencing at both the chromosomal HMRa locus and the extrachromosomal HMRa locus with equal efficiency. Thus, in contrast to the prevailing view, the establishment of silencing occurred in the absence of passage of the DNA replication fork through or near the HMR locus, but retained a cell cycle dependence.
Kirchmaier
A L
AL
Division of Genetics and Development, Department of Molecular and Cell Biology, University of California, 401 Barker Hall, Berkeley, CA 94720, USA.
Rine
J
J
D001665:Binding Sites; D015825:Chromosomes, Fungal / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D016193:G1 Phase; D020868:Gene Silencing; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D006570:Heterochromatin / Q000737:chemistry / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics; D010675:Pheromones; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D018741:Replication Origin; D016196:S Phase; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006570:Heterochromatin; D008074:Lipoproteins; C095063:MFA2 protein, S cerevisiae; D010675:Pheromones; D011993:Recombinant Fusion Proteins; C084121:SIR1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D004254:DNA Nucleotidyltransferases; C045119:FLP recombinase