title: Fission yeast Mes1p ensures the onset of meiosis II by blocking degradation of cyclin Cdc13p.
abstract: Meiosis is a special form of nuclear division to generate eggs, sperm and spores in eukaryotes. Meiosis consists of the first (MI) and the second (MII) meiotic divisions, which occur consecutively. MI is reductional, in which homologous chromosomes derived from parents segregate. MI is supported by an elaborate mechanism involving meiosis-specific cohesin and its protector. MII is equational, in which replicated sister-chromatids separate as in mitosis. MII is generally considered to mimic mitosis in mechanism. However, fission yeast Mes1p is essential for MII but dispensable for mitosis. The mes1-B44 mutant arrests before MII. Transcription of mes1 is low in vegetative cells and boosted in a narrow window between late MI and late MII. The mes1 mRNA undergoes meiosis-specific splicing. Here we show that Mes1p is a factor that suppresses the degradation of cyclin Cdc13p at anaphase I. Mes1p binds to Slp1p, an activator of APC/C (anaphase promoting complex/cyclosome), and counteracts its function to engage Cdc13p in proteolysis. Inhibition of APC/C-dependent degradation of Cdc13p by Mes1p was reproduced in a Xenopus egg extract. We therefore propose that Mes1p has a key function in saving a sufficient level of MPF (M-phase-promoting factor) activity required for the execution of MII.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, Tokyo 113-0033, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Izawa
authors.forename: Masuo
authors.initials: M
authors.lastname: Goto
authors.forename: Akira
authors.initials: A
authors.lastname: Yamashita
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamano
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D000483:Alleles; D000705:Anaphase; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D002457:Cell Extracts; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase; D006657:Histones / Q000378:metabolism; D008540:Meiosis; D008677:Metaphase; D009154:Mutation / Q000235:genetics; D009865:Oocytes; D016366:Open Reading Frames / Q000235:genetics; D011485:Protein Binding; D012568:Schizosaccharomyces / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D064249:Securin; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism; D014982:Xenopus laevis; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism
chemical_list: C498823:Cdc13 protein, S pombe; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D002457:Cell Extracts; C080328:Cig2 protein, S pombe; C103136:Cut2 protein, S pombe; D019926:Cyclin B; D016213:Cyclins; D005656:Fungal Proteins; D006657:Histones; C432695:Mes1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D064249:Securin; D020666:ras-GRF1; C577504:slp1 protein, S pombe; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D016203:CDC2 Protein Kinase