Abstract

The cyc1-512 mutation is a 38 base pair deletion in the 3' nontranslated region of the CYC1 locus in the yeast Saccharomyces cerevisiae. The deletion occurred between two 7 bp directly repeated sequences. The cyc1-512 mutant produces approximately 10% of the normal amount of the CYC1 gene product, iso-1-cytochrome c, and produces 5%--10% of the normal steady-state amount of CYC1 mRNA. Most of the mRNAs in cyc1-512 are longer at their 3' ends by up to 1000 nucleotides, suggesting that the 38 bp deletion in cyc1-512 prevents proper transcription termination. The improper transcription termination is shown to cause converging transcription between CYC1 and an adjacent gene. The fact that all of the aberrantly sized mRNAs in cyc1-512 are polyadenylated leads us to suggest that polyadenylation may be coupled to transcription termination in yeast. We have uncovered a consensus sequence between the region deleted in cyc1-512 and the 3' nontranslated regions of some but not all yeast genes, and discuss the possible role of this sequence in transcription termination.