Positive regulation of transcription of homeoprotein-encoding YHP1 by the two-component regulator Sln1 in Saccharomyces cerevisiae.

The IME1 gene is essential for initiation of meiosis in Saccharomyces cerevisiae. Transcription of IME1 is induced under starvation for nitrogen and glucose and in the presence of the MATa1 and MATalpha2 gene products. We have shown in our previous work that homeoprotein Yhp1 binds to a 28-bp region between nt -702 and -675 of the IME1 promoter in vivo and in vitro. We also revealed that the 28-bp region fused with a reporter gene harbored Yhp1-dependent URS (upstream repression sequence) activity and that the transcription of YHP1 was repressed by nonfermentable carbon source. In this study, we found, using a 5'-deletion series of the YHP1 promoter fused with a reporter gene, that the URS responsible for repression of YHP1 transcription with a nonfermentable carbon source is located at a region from nt -696 to -466 of the YHP1 promoter. We also identified and delimited a UAS (upstream activation sequence), which confers activation in both fermentable and nonfermentable carbon source media, to be from nt -356 to -306 of the YHP1 promoter. The UAS of the YHP1 promoter contained an MCE (Mcm1 control element) that is a target of the general transcription factor Mcm1 and is known to be involved in positive regulation by the two-component regulator Sln1. Consistent with this fact, the YHP1 transcription level was reduced in the Deltasln1 mutant, indicating that the two-component regulator Sln1 is involved in activation of YHP1 transcription.