Two new S-phase-specific genes from Saccharomyces cerevisiae.
Two new yeast genes, ASF1 (Anti-Silencing Function) and ASF2, as well as a C-terminal fragment of SIR3, were identified as genes that derepressed the silent mating type loci when overexpressed. ASF2 overexpression caused a greater derepression than did ASF1. ASF1 overexpression also weakened repression of genes near telomeres, but, interestingly, ASF2 had no effect on telomeric silencing. Sequences of these two genes revealed open reading frames of 279 and 525 amino acids for ASF1 and ASF2, respectively. The ASF1 protein was evolutionarily conserved, MCB motifs, sequences commonly present upstream of genes transcribed specifically in S phase, were found in front of both genes, and, indeed, both genes were transcribed specifically in the S phase of the cell cycle. While an asf2 mutant was viable and had no obvious phenotypes, an asf1 mutant grew poorly. Neither mutant exhibited derepression of the silent mating type loci. The asf1 mutant was sensitive to methyl methane sulfonate, slightly UV-sensitive and somewhat deficient in minichromosome maintenance. It also lowered the restrictive temperature of a cdc13ts mutant. These phenotypes suggested a role for ASF1 in DNA repair and chromosome maintenance.
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Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794, USA.
Davis
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C
Konopka
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JB
Sternglanz
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D000595:Amino Acid Sequence; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D019926:Cyclin B / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000528:radiation effects; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010957:Plasmids; D016196:S Phase / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins; D017422:Sequence Analysis, DNA; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D016615:Telomere / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014170:Transformation, Genetic; D014466:Ultraviolet Rays
C109731:ASF1 protein, S cerevisiae; C109732:ASF2 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D005656:Fungal Proteins; D018832:Molecular Chaperones; C084122:SIR3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D038281:Silent Information Regulator Proteins, Saccharomyces cerevisiae; D015534:Trans-Activators; D008741:Methyl Methanesulfonate