SNF6 ENCODES A NUCLEAR-PROTEIN THAT IS REQUIRED FOR EXPRESSION OF MANY GENES IN SACCHAROMYCES-CEREVISIAE

The SNF6 gene appears to affect transcription from a variety of promoters in Saccharomyces cerevisiae. The gene was cloned, and sequence analysis revealed two completely overlapping open reading frames of 996 and 1092 nucleotides on opposite strands. The SNF6 coding sequence was identified by selective mutagenesis. The predicted 37,604-dalton SNF6 protein is highly charged but overall neutral. A bifunctional SNF6-β-galactosidase fusion protein was localized in the nucleus, as judged by immunofluorescence microscopy. The N terminus of SNF6 contains a sequence homologous to nuclear localization signals and was sufficient to direct β-galactosidase to the nucleus. The 5' ends of the SNF6 RNA wre heterogeneous and included ends mapping downstream from the first ATG codon. Construction of a frameshift mutation provided evidence that translational initiation at the second ATG yields a partially functional SNF6 product. Null mutations in SNF6 caused a wider range of pleiotropic defects than the previously isolated point mutation, including slow growth. Genetic and molecular evidence suggested that SNF6 is functionally related to the SNF2 and SNF5 genes. These genes may function together to affect transcription.