title: A Cds1-mediated checkpoint protects the MBF activator Rep2 from ubiquitination by anaphase-promoting complex/cyclosome-Ste9 at S-phase arrest in fission yeast.
abstract: Transcription of the MluI cell cycle box (MCB) motif-containing genes at G(1) phase is regulated by the MCB-binding factors (MBF) (also called DSC1) in Schizosaccharomyces pombe. Upon S-phase arrest, the MBF transcriptional activity is induced through the accumulation of the MBF activator Rep2. In this study, we show that the turnover of Rep2 is attributable to ubiquitin-mediated proteolysis. Levels of Rep2 oscillate during the cell cycle, with a peak at G(1) phase, coincident with the MBF activity. Furthermore, we show that Rep2 ubiquitination requires the function of the E3 ligase anaphase-promoting complex/cyclosome (APC/C). Ste9 can be phosphorylated by the checkpoint kinase Cds1 in vitro, and its inhibition/phosphorylation at S-phase arrest is dependent on the function of Cds1. Our data indicate that the Cds1-dependent stabilization of Rep2 is achieved through the inhibition/phosphorylation of APC/C-Ste9 at the onset of S-phase arrest. Stabilization of Rep2 is important for stimulating transcription of the MBF-dependent genes to ensure a sufficient supply of proteins essential for cell recovery from S-phase arrest. We propose that oscillation of Rep2 plays a role in regulation of periodic transcription of the MBF-dependent genes during cell cycle progression.
authors: Systems Biology, Genome Institute of Singapore, A*STAR, Biopolis, Singapore, Singapore.
authors: Zhaoqing
authors: Z
authors: Chu
authors: Majid
authors: M
authors: Eshaghi
authors: Suk Yean
authors: SY
authors: Poon
authors: Jianhua
authors: J
authors: Liu
mesh_terms: D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D018797:Cell Cycle Proteins / Q000378:metabolism*; D064447:Checkpoint Kinase 2; D004268:DNA-Binding Proteins / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects; D006918:Hydroxyurea / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D055550:Protein Stability / Q000187:drug effects; D016196:S Phase / Q000187:drug effects; D012568:Schizosaccharomyces / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C096254:Rep2 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D015534:Trans-Activators; C087021:res2 protein, S pombe; C113000:srw1 protein, S pombe; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D064447:Checkpoint Kinase 2; C578636:Cds1 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; D006918:Hydroxyurea