title: MCB-mediated regulation of cell cycle-specific cdc22+ transcription in fission yeast.
abstract: The cdc22+ gene of the fission yeast, Schizosaccharomyces pombe, encodes the large subunit of ribonucleotide reductase, and is periodically expressed during the mitotic cell cycle, transcript abundance reaching a maximum at the G1-S boundary. This regulation of expression is controlled by a transcription factor complex called DSC1, which binds to MCB motifs (ACGCGT) present in the promoter of cdc22+. cdc22+ has a complex pattern of MCBs, including two clusters of four motifs each, one of which is located within the transcribed region. We show that both clusters of MCBs contribute to the regulation of cdc22+ expression during the cell cycle, each having a different role. The MCB cluster within the transcribed region has the major role in regulating cdc22+, as its removal results in loss of transcription. The upstream cluster, instead, controls cell cycle-specific transcription through a negative function, as its removal results in expression of cdc22+ throughout the cell cycle. Both MCB clusters bind DSC1. We show that the interaction of DSC1 with the MCB cluster within the transcribed region has a high "on-off" rate, suggesting a mechanism by which DSC1 could activate expression, and still allow RNA polymerase to pass during transcription. Finally, we show that both clusters are orientation-dependent in their function. The significance of these results, in the context of MCB-mediated regulation of G1-S expression in fission yeast, is discussed.
authors.affiliation: Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, Glasgow, Scotland.
authors.forename: Z
authors.initials: Z
authors.lastname: Maqbool
authors.forename: P J
authors.initials: PJ
authors.lastname: Kersey
authors.forename: P A
authors.initials: PA
authors.lastname: Fantes
authors.forename: C J
authors.initials: CJ
authors.lastname: McInerny
mesh_terms: D001483:Base Sequence; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D018983:DNA Footprinting; D012321:DNA-Directed RNA Polymerases; D016193:G1 Phase; D020558:GTP Phosphohydrolases; D015966:Gene Expression Regulation, Fungal; D008562:Membrane Glycoproteins / Q000235:genetics; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012264:Ribonucleotide Reductases; D016196:S Phase; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: C090459:CDC1 protein, S cerevisiae; D018797:Cell Cycle Proteins; C489911:DSC1 protein, S pombe; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C061178:cdc10 protein, S pombe; C080926:cdc22 protein, S pombe; D012264:Ribonucleotide Reductases; D012321:DNA-Directed RNA Polymerases; C512892:CDC10 protein, S cerevisiae; D020558:GTP Phosphohydrolases