An Ssn6-Tup1-dependent negative regulatory element controls sporulation-specific expression of DIT1 and DIT2 in Saccharomyces cerevisiae

作者：Friesen H; Hepworth SR; Segall J

来源：Molecular and Cellular Biology, 1997, 17(1): 123-134.

Sporulation of the yeast Saccharomyces cerevisiae is a process of cellular differentiation that occurs in MATa/MAT alpha diploid cells in response to starvation. The sporulation-specific genes DIT1 and DIT2, which are required for spore wall formation, are activated midway through the sporulation program, with maximal transcript accumulation occurring at the time of prospore enclosure, In this study, we have identified a negative regulatory element, termed NRE(DIT), that is located between the start sites of transcription of these divergently transcribed genes. This element, which prevents expression of the DIT1 and DIT2 genes during vegetative growth, reduces expression of a CYC1-lacZ reporter gene more than 1,000-fold and acts in an orientation- and position-independent manner. We found that the ability of NRE(DIT) to turn off expression of the reporter gene and the chromosomal DIT1 and DIT2 genes in vegetative cells requires the Ssn6-Tup1 repression complex. Interestingly, NRE(DIT)-mediated repression of the reporter gene is maintained during sporulation, Derepression during sporulation requires complex interactions among several cis-acting elements. These are present on an similar to 350-bp DNA fragment extending from NRE(DIT) to the TATA box and an similar to 125-bp fragment spanning the TATA box of DIT1. Additionally, a region of NRE(DIT) which is very similar in sequence to UAS(SPS4), an element that activates gene expression midway through sporulation, contributes both to vegetative repression and to sporulation-specific induction of DIT1. We propose a model to explain the requirement for multiple elements in overcoming NRE(DIT)-mediated repression during sporulation.

• 出版日期1997-1