The Zinc Cluster Protein Sut1 Contributes to Filamentation in Saccharomyces cerevisiae
ABSTRACTSut1 is a transcriptional regulator of the Zn(II)2Cys6family in the budding yeastSaccharomyces cerevisiae. The only function that has been attributed to Sut1 is sterol uptake under anaerobic conditions. Here, we show that Sut1 is also expressed in the presence of oxygen, and we identify a novel function for Sut1.SUT1overexpression blocks filamentous growth, a response to nutrient limitation, in both haploid and diploid cells. This inhibition by Sut1 is independent of its function in sterol uptake. Sut1 downregulates the expression ofGAT2,HAP4,MGA1,MSN4,NCE102,PRR2,RHO3, andRHO5. Several of these Sut1 targets (GAT2,HAP4,MGA1,RHO3, andRHO5) are essential for filamentation in haploids and/or diploids. Furthermore, the expression of the Sut1 target genes, with the exception ofMGA1, is induced during filamentous growth. We also show thatSUT1expression is autoregulated and inhibited by Ste12, a key transcriptional regulator of filamentation. We propose that Sut1 partially represses the expression ofGAT2,HAP4,MGA1,MSN4,NCE102,PRR2,RHO3, andRHO5when nutrients are plentiful. Filamentation-inducing conditions relieve this repression by Sut1, and the increased expression of Sut1 targets triggers filamentous growth.