THE YEAST RME1 GENE ENCODES A PUTATIVE ZINC FINGER PROTEIN THAT IS DIRECTLY REPRESSED BY A1-ALPHA-2

In the yeast Saccharomyces cerevisiae, a/alpha cells can enter meiosis whereas a and alpha-cells cannot. The a/alpha-cell type is determined by presence of a repressor, a-1-alpha-2. Previous studies indicate that a/alpha-cells lack an inhibitor of meiosis, the RME1 gene product, and that a and alpha-cells express RME1. We report here the sequence of RME1 and functional analysis of its regulatory and coding regions. The 5'-region of RME1 includes a sequence resembling a1-alpha-2 repression sites. Deletion of this site at RME1 relieves repression by a1-alpha-2, and insertion of the site into a heterologous regulatory region (CYC1) confers weak repression in a/alpha-cells. These observations indicate that RME1 is directly repressed by a1-alpha-2. The RME1 product has three regions that resemble C2H2 zinc fingers, which are characteristic of a class of nucleic-acid-binding proteins. Substitution of serine for cysteine in each of the putative fingers abolishes RME1 function; serine substitutions in the second and third putative fingers do not affect RME1 stability. These findings indicate that at least two putative zinc fingers are critical for RME1 structure or activity. Therefore RME1, which is formally a negative regulator of the meiotic gene IME1, may act directly as a repressor.