Regulation of the premiddle and middle phases of expression of the NDT80 gene during sporulation of Saccharomyces cerevisiae.
The NDT80 gene of Saccharomyces cerevisiae, which encodes a global activator of transcription of middle sporulation-specific genes, is first expressed after the activation of early meiotic genes but prior to activation of middle sporulation-specific genes. Both upstream repression sequence 1 (URS1) and mid-sporulation element (MSE) sites are present in the promoter region of the NDT80 gene; these elements have been shown previously to contribute to the regulation of expression of early and middle sporulation-specific genes, respectively, by mediating repression in growing cells and activation at specific times during sporulation. In this study, we have shown that the overlapping windows of URS1- and MSE-mediated repression and activation are responsible for the distinctive premiddle expression pattern of the NDT80 gene. Our data suggest that a Sum1-associated repression complex bound at the NDT80 MSE sites prevents Ime1 tethered at the NDT80 URS1 sites from activating transcription of the NDT80 gene at the time that Ime1-dependent activation of early URS1-regulated meiotic genes is occurring. We propose that a decrease in the efficiency of Sum1-mediated repression as cells progress through the early events of the sporulation program allows the previously inactive Ime1 tethered at the URS1(NDT80) sites to promote a low level of expression of the NDT80 gene. This initial phase of URS1-dependent NDT80 expression is followed by Ndt80-dependent upregulation of its own expression, which requires the MSE(NDT80) sites and occurs concomitantly with Ndt80-dependent activation of a set of middle MSE-regulated sporulation-specific genes. Mutation of IME2 prevents expression of NDT80 in sporulating cells. We show in this study that NDT80 is expressed and that middle genes are activated in cells of an Deltaime2/Deltaime2 Deltasum1/Deltasum1 strain in sporulation medium. This suggests that Ime2 activates expression of NDT80 by eliminating Sum1-mediated repression.
Department of Molecular and Medical Genetics, University of Toronto, Ontario, Canada M5S 1A8.
Julia
J
Pak
Jacqueline
J
Segall
D015152:Blotting, Northern; D002455:Cell Division; D004268:DNA-Binding Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D008540:Meiosis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008938:Mitosis; D008957:Models, Genetic; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012313:RNA / Q000378:metabolism; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C097071:NDT80 protein, S cerevisiae; D009687:Nuclear Proteins; D012097:Repressor Proteins; C100925:SUM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C089979:UME6 protein, S cerevisiae; D012313:RNA; D020928:Mitogen-Activated Protein Kinases; C443670:Smk1 protein, S cerevisiae; D001616:beta-Galactosidase