The pachytene checkpoint in Saccharomyces cerevisiae requires the Sum1 transcriptional repressor.
Saccharomyces cerevisiae mutants that fail to complete meiotic recombination are blocked by the RAD17/RAD24/MEC1 checkpoint signaling pathway in pachytene when early sporulation genes are expressed. Middle genes are not activated in checkpoint-arrested cells because the Ndt80 transcription factor is inhibited. We find that the pachytene checkpoint requires Sum1, a transcriptional repressor that recognizes a subset of Ndt80-binding sites. Mutants lacking Sum1 or Rad17 partially bypass the block to the nuclear divisions but do not form spores, while mutants lacking both Sum1 and Rad17 completely bypass the block and form morphologically normal spores. The level of Sum1 protein decreases as middle genes are expressed, and this decrease is blocked in checkpoint-arrested cells. These data suggest that Sum1 levels are regulated by the checkpoint and that progression of the meiotic divisions and spore differentiation can be differentially controlled by competition of the Sum1 repressor and Ndt80 activator for occupancy at key middle promoters.
Lindgren
A
A
Department of Biochemistry and Molecular Pharmacology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Bungard
D
D
Pierce
M
M
Xie
J
J
Vershon
A
A
Winter
E
E
D015152:Blotting, Northern; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000378:metabolism; D006655:Histone Deacetylases; D047908:Intracellular Signaling Peptides and Proteins; D008540:Meiosis; D008856:Microscopy, Fluorescence; D008858:Microscopy, Phase-Contrast; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases; D011995:Recombination, Genetic; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D056565:Sirtuin 2; D037761:Sirtuins; D013172:Spores, Fungal / Q000502:physiology / Q000648:ultrastructure; D013997:Time Factors; D014157:Transcription Factors; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; C097071:NDT80 protein, S cerevisiae; D009687:Nuclear Proteins; C501395:RAD17 protein, S cerevisiae; C088385:RAD24 protein, S cerevisiae; D012097:Repressor Proteins; C100925:SUM1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C088937:MEC1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C103934:HST1 protein, S cerevisiae; D056565:Sirtuin 2; D037761:Sirtuins; D006655:Histone Deacetylases