A COMMON ELEMENT INVOLVED IN TRANSCRIPTIONAL REGULATION OF 2 DNA ALKYLATION REPAIR GENES (MAG AND MGT1) OF SACCHAROMYCES-CEREVISIAE

The Sacharomyces cerevisiae MAG gene encodes a 3-methyladenine DNA gly cosylase that protects cells from killing by alkylating agents. MAG mR NA levels are induced not only by alkylating agents but also by DNA-da maging agents that do not produce alkylated DNA. We constructed a MAG- lacZ gene fusion to help identify the cis-acting promoter elements inv olved in regulating MAG expression. Deletion analysis defined the pres ence of one upstream activating sequence and one upstream repressing s equence (URS) and suggested the presence of a second URS. One of the M AG URS elements matches a decamer consensus sequence present in the pr omoters of 11 other S. cerevisiae DNA repair and metabolism genes, inc luding the MGT1 gene, which encodes an O6-methylguanine DNA repair met hyltransferase. Two proteins of 26 and 39 kDa bind specifically to the MAG and MGT1 URS elements. We suggest that the URS-binding proteins m ay play an important role in the coordinate regulation of these S. cer evisiae DNA repair genes.