Participation of the Yeast Activator Abf1 in Meiosis-Specific Expression of the HOP1 Gene

Abstract

The meiosis-specific gene HOP1, which encodes a component of the synaptonemal complex, is controlled through two regulatory elements, UAS(H) and URS(H). Sites similar to URSI(H) have been identified in the promoter regina of virtually every early meiosis-specific gene, as well as in many promoters of nonmeiotic genes, and it has been shown that the proteins that bind to this site function to regulate meiotic and nonmeiotic transcription. Sites similar to the UAS(H) site have been found in a number of meiotic and nonmeiotic genes as well. Since it has been shown that UAS(H) functions as an activator site in vegetative haploid cells, it seemed likely that the factors binding to this site regulate both meiotic and nonmeiotic transcription. We purified the factor binding to the UAS(H) element of the HOP1 promoter. Sequence analysis identified the protein as Abf1 (autonomously replicating sequence-binding factor 1), a multifunctional protein involved in DNA replication, silencing, and transcriptional regulation. We show by mutational analysis of the UAS(H) site, that positions outside of the proposed UAS(H) consensus sequence (TNTGN[A/T]GT) are required for DNA binding in vitro and transcriptional activation in vivo. A new UAS(H) consensus sequence derived from this mutational analysis closely matches a consensus Abf1 binding site. We also show that an Abf1 site from a nonmeiotic gene can replace the function of the UAS(H) site in the HOP1 promoter. Taken together, these results show that Abf1 functions to regulate meiotic gene expression.