Domains of the SFL1 protein of yeasts are homologous to Myc oncoproteins or yeast heat-shock transcription factor

We identified a yeast suppressor gene for flocculation ( SFL1 ), which complemented a newly isolated sfl1 mutant. This mutation causes asexual cell aggregation. SFL 1 encodes a 767-amino acid protein which has two domains significantly homologous to Myc oncoproteins and the yeast heat shock transcription factor (HSTF). The Myc homologous region in SFL 1 overlaps with the conserved region m a series of interesting proteins: MyoD1, Drosophila achaete-scute, twist, daughterless gene products and immunoglobulin enhancer-binding proteins. In addition, the N-terminal region of the SFL1 gene product shows extensive homology to the DNA-binding domain of HSTF. Mutational analysis of SFL1 demonstrates that it is required for normal cell-surface assembly in vegetative growth. We propose that the SFL 1 gene product may be a transcription factor which is involved in regulation of the gene(s) related to yeast flocculation.