TRANSCRIPTIONAL REGULATION OF THE SMK1 MITOGEN-ACTIVATED PROTEIN-KINASE GENE DURING MEIOTIC DEVELOPMENT IN SACCHAROMYCES-CEREVISIAE

Meiotic development (sporulation) in Saccharomyces cerevisiae is chara cterized by an ordered pattern of gene expression, with sporulation-sp ecific genes classified as early, middle, mid-late, or late depending on when they are expressed. SMK1 encodes a mitogen-activated protein k inase required for spore morphogenesis that is expressed as a middle s porulation-specific gene, Here, we identify the cis-acting DNA element s that regulate SMK1 transcription and characterize the phenotypes of mutants with altered expression patterns. The SMK1 promoter contains a n upstream activating sequence (UAS(S)) that specifically interacts wi th the transcriptional activator Abf1p. The Abf1p-binding sites from t he early HOP1 and the middle SMK1 promoters are functionally interchan geable, demonstrating that these elements do not play a direct role in their differential transcriptional timing. Timing of SMK1 expression is determined by another cis-acting DNA sequence termed MSE (for middl e sporulation element). The MSE is required not only for activation of SMK1 transcription during middle sporulation but also for its repress ion during vegetative growth and early meiosis, In addition, the SMK1 MSE can repress vegetative expression in the context of the HOPI promo ter and convert HOPI from an early to a middle gene. SMK1 function is not contingent on its tight transcriptional regulation as a middle spo rulation-specific gene. However, promoter mutants with different quant itative defects in SMK1 transcript levels during middle sporulation sh ow distinct sporulation phenotypes.