CHARACTERIZATION OF A SHORT UNIQUE SEQUENCE IN THE YEAST HO GENE PROMOTER THAT REGULATES HO TRANSCRIPTION IN A SIN1 DEPENDENT MANNER

Recently it has become clear that general chromatin proteins as well a s sequence-specific DNA binding proteins are important in the control of gene expression, SIN1 in Saccharomyces cerevisiae is a chromatin co mponent that regulates the transcription of a family of genes, Previou sly, we identified a 32 bp unique sequence (here termed XBS) in the pr omoter of one of those genes, HO, which specifically binds a protein t hat interacts with SIN1, We also found that this sequence can function as a weak UAS in a heterologous promoter that is dependent on the pre sence of SIN1, Here we report a relationship between the level of 80 e xpression and the presence of the short sequence in situ in the HO gen e, By comparing the expression of HO from mild type or XBS deleted HO promoters, we concluded that XBS serves as a weak UAS in situ in the H O gene, that it influences HO transcription via the SWI/SNF complex, a nd that sequences other than the XBS mediate the affect of SIN1 on HO transcription, In addition, we show that a portion of the SIN1 protein that has sequence similarity to mammalian HMG1 preferentially binds t he XBS.