SACCHAROMYCES-CEREVISIAE BUF PROTEIN BINDS TO SEQUENCES PARTICIPATINGIN DNA-REPLICATION IN ADDITION TO THOSE MEDIATING TRANSCRIPTIONAL REPRESSION (URS1) AND ACTIVATION

The heteromeric BUF protein was originally shown to bind to URS1 eleme nts which are situated upstream of many genes in Saccharomyces cerevis iae and mediate negative control of their transcription. Among the gen es regulated through the URS1 site and the proteins interacting with i t are those participating in carbon, nitrogen, and inositol metabolism ; electron transport; meiosis; sporulation; and mating-type switching. We show here that pure BUF protein, in addition to binding to the neg atively acting URS1 site, also binds to CAR1 sequences supporting tran scriptional activation (upstream activation sequences). To determine t he BUF protein structure, we cloned and sequenced the BM and BUF2 gene s and found them to be identical to the RF-A (RP-A) genes whose produc ts participate in yeast DNA replication as single-stranded DNA binding proteins. These data argue that BUF protein-binding sites serve multi ple roles in transcription and replication.