Genetic analysis of the YDR1-BUR6 repressor complex reveals an intricate balance among transcriptional regulatory proteins in yeast.
A transcriptional repressor complex encoded by two essential genes, YDR1 and BUR6, was isolated from Saccharomyces cerevisiae and shown to be the functional counterpart of the human repressor complex Dr1-DRAP1. To elucidate the mechanism of repression by this complex, altered forms of Ydr1 and Bur6 were studied in vitro and ... in vivo. Deletion of the C-terminal 41 amino acids of Ydr1 resulted in loss of repressor activity and a growth defect, suggesting that the C-terminal domain of Ydr1 functions as a potent transcriptional repressor. A screen for extragenic suppressors of a cold-sensitive ydr1 (ydr1(cs)) mutant led to the identification of recessive mutations in the SIN4 gene, which encodes a component of the SRB-MED complex. The sin4 alleles suppressed not only ydr1(cs) mutations but also bur6(cs) mutations. In contrast, deletion of the gal11 gene, whose product is also a member of the SRB-MED complex, failed to suppress ydr1(cs) and bur6(cs) mutations, indicating that suppression is not due to general defects in the SRB-MED complex. Moreover, one of the sin4 alleles, but not the sin4 deletion, was found to specifically suppress the inviability of a ydr1 deletion, demonstrating that the essential function of Ydr1 becomes dispensable in a sin4 mutant background. Biochemical analysis of the SRB-MED complex from the sin4 suppressor strain revealed a structurally distinct form of the SRB-MED complex that lacks a subset of mediator subunits. These results define a delicate balance between positive and negative regulators of transcription operating through the Ydr1-Bur6 repressor complex.
Mesh Terms:
ATP-Binding Cassette Transporters, Amino Acid Sequence, Fungal Proteins, Gene Expression Regulation, Fungal, Genes, Fungal, Genotype, Humans, Mediator Complex, Molecular Sequence Data, Mutation, Phosphoproteins, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Alignment, Trans-Activators, Transcription Factors
ATP-Binding Cassette Transporters, Amino Acid Sequence, Fungal Proteins, Gene Expression Regulation, Fungal, Genes, Fungal, Genotype, Humans, Mediator Complex, Molecular Sequence Data, Mutation, Phosphoproteins, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Sequence Alignment, Trans-Activators, Transcription Factors
Mol. Cell. Biol.
Date: Apr. 01, 2000
PubMed ID: 10713169
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