Multiple and Distinct Activation and Repression Sequences Mediate the Regulated Transcription of IME1, a Transcriptional Activator of Meiosis-Specific Genes in Saccharomyces cerevisiae

Abstract

IME1 encodes a transcriptional activator required for the transcription of meiosis-specific genes and initiation of meiosis in Saccharomyces cerevisiae. The transcription of IME1 is repressed in the presence of glucose, and a low basal level of IME1 RNA is observed in vegetative cultures with acetate as the sole carbon source. Upon nitrogen depletion a transient induction in the transcription of IME1 is observed in MATa/MAT␣ diploids but not in MAT-insufficient strains. In this study we demonstrate that the transcription of IME1 is controlled by an extremely unusual large 5 region, over 2,100 bp long. This area is divided into four different upstream controlling sequences (UCS). UCS2 promotes the transcription of IME1 in the presence of a nonfermentable carbon source. UCS2 is flanked by three negative regions: UCS1, which exhibits URS activity in the presence of nitrogen, and UCS3 and UCS4, which repress the activity of UCS2 in MAT-insufficient cells. UCS2 consists of alternate positive and negative elements: three distinct constitutive URS elements that prevent the function of any upstream activating sequence (UAS) under all growth conditions, a constitutive UAS element that promotes expression under all growth conditions, a UAS element that is active only in vegetative media, and two discrete elements that function as UASs in the presence of acetate. Sequence analysis of IME1 revealed the presence of two almost identical 30-to 32-bp repeats. Surprisingly, one repeat, IREd, exhibits constitutive URS activity, whereas the other repeat, IREu, serves as a carbon-source-regulated UAS element. The RAS-cyclic AMP-dependent protein kinase cAPK pathway prevents the UAS activity of IREu in the presence of glucose as the sole carbon source, while the transcriptional activators Msn2p and Msn4p promote the UAS activity of this repeat in the presence of acetate. We suggest that the use of multiple negative and positive elements is essential to restrict transcription to the appropriate conditions and that the combinatorial effect of the entire region leads to the regulated transcription of IME1.In the budding yeast Saccharomyces cerevisiae the choice between meiosis-sporulation and alternative developmental pathways such as the mitotic cell cycle, pseudohyphae growth, or G 1 arrest depends on the expression and activity of a master regulator, Ime1p. This is deduced from the observation that cells deleted for IME1 are sporulation deficient and arrest in meiosis at G 1 prior to any meiotic event, i.e., transcription of meiosis-specific genes, premeiotic DNA replication, meiotic recombination, and nuclear divisions (15, 49). IME1 encodes a transcriptional activator (23, 48) that is recruited to the promoters of early meiosis-specific genes by interacting with a sequence-specific DNA binding protein, Ume6p (41).Initiation of meiosis depends on two signals: starvation for nutrients and the presence of MATa1 and MAT␣2 gene products (17). The nutrient signal is required at several levels: for the transcription of IME1 (15), for the...

Multiple Pathways Are Co-regulated by the Protein Kinase Snf1 and the Transcription Factors Adr1 and Cat8

“…IME1 is a master regulator of meiotic-specific gene expression. It has a large and complex upstream regulatory region that controls its activity in response to ploidy and growth conditions (53). Its known activity is important only in diploids undergoing meiosis.…”

Functional Dissection of IME1 Transcription Using Quantitative Promoter–Reporter Screening

“…Dissection of IME1 Promoterof known consensus binding sites to predict the TFs that may bind to the 2117-bp regulatory region of the IME1 gene (Sagee et al 1998). We discovered 75 putative TFs, present on 346 sites, which showed a perfect match to the reported consensus sites.…”

“…IREu is an important but nonconserved element in the IME1 promoter: The S. cerevisiae IME1 promoter carries two short repeats designated IREu and IREd in which 30 of the 32 bp are identical (Sagee et al 1998) ( Figure 3A). The IREd repeat is conserved in S. paradoxus and S. bayanus, but the IREu repeat is absent ( Figure 3B).…”

“…This means that most genes are not suitable for such an analysis. However, complex regulation by an exceptionally large region can be found at the IME1 gene (.2 kb) (Granot et al 1989;Sagee et al 1998). IME1 encodes a transcriptional activator that serves as the master regulator of meiosis in budding yeast.…”

“…Deletion analysis of the 59 regulatory region of the IME1 gene revealed that it is regulated by at least 10 distinct elements, 6 of which confer negative regulation, while 4 confer positive regulation ( Figure 1; . However, knowledge of the DNA-binding proteins that directly affect transcription of the IME1 promoter remains incomplete with only a few known regulators (Msn2/4, Rme1, Sok2, and Yhp1) (Sagee et al 1998;Shimizu et al 1998;Kunoh et al 2000;Shenhar and Kassir 2001).…”