Molecular mechanisms underlying the mitosis-meiosis decision

Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Chromosome Research (Impact Factor: 2.48). 02/2007; 15(5):523-37. DOI: 10.1007/s10577-007-1151-0
Source: PubMed


Most eukaryotic cells possess genetic potential to perform meiosis, but the vast majority of them never initiate it. The entry to meiosis is strictly regulated by developmental and environmental conditions, which vary significantly from species to species. Molecular mechanisms underlying the mitosis-meiosis decision are unclear in most organisms, except for a few model systems including fission yeast Schizosaccharomyces pombe. Nutrient limitation is a cue to the entry into meiosis in this microbe. Signals from nutrients converge on the activity of Mei2 protein, which plays pivotal roles in both induction and progression of meiosis. Here we outline the current knowledge of how a set of environmental stimuli eventually activates Mei2, and discuss how Mei2 governs the meiotic program molecularly, especially focusing on a recent finding that Mei2 antagonizes selective elimination of meiotic messenger RNAs.

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    • "RNA-based chromatin regulation of entry into meiosis in S. pombe Induction of sporulation: similarities and distinctions in comparison to S. cerevisiae Induction of sporulation in the fission yeast S. pombe, like S. cerevisiae, is under the control of signaling pathways monitoring the status of the yeast mating type and sensing nutrients availability (mainly nitrogen) (Harigaya and Yamamoto 2007; Otsubo and Yamamoto 2012 "
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    ABSTRACT: Germ cell differentiation, the cellular process by which a diploid progenitor cell produces by meiotic divisions haploid cells, is conserved from the unicellular yeasts to mammals. Over the recent years, yeast germ cell differentiation process has proven to be a powerful biological system to identify and study several long noncoding RNAs (lncRNAs) that play a central role in regulating cellular differentiation by acting directly on chromatin. Remarkably, in the well-studied budding yeast Saccharomyces cerevisiae and fission yeast Schizosaccharomyces pombe, the lncRNA-based chromatin regulations of germ cell differentiation are quite different. In this review, we present an overview of these regulations by focusing on the mechanisms and their respective functions both in S. cerevisiae and in S. pombe. Part of these lncRNA-based chromatin regulations may be conserved in other eukaryotes and play critical roles either in the context of germ cell differentiation or, more generally, in the development of multicellular organisms.
    Full-text · Article · Nov 2013 · Chromosome Research
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    • "This global change of gene expression is carried out through posttranscriptional regulation in addition to transcriptional regulation. In the fission yeast Schizosaccharomyces pombe, an RNA-binding protein, Mmi1, plays a crucial role in selectively eliminating meiosis-specific transcripts in mitotic cells (3,4). Mmi1 belongs to the YTH family (5) and recognizes a region termed the determinant of selective removal (DSR), which is enriched with repeats of hexanucleotide motifs (6). "
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    ABSTRACT: A number of meiosis-specific transcripts are selectively eliminated during the mitotic cell cycle in fission yeast. Mmi1, an RNA-binding protein, plays a crucial role in this selective elimination. Mmi1 recognizes a specific region, namely, the determinant of selective removal (DSR) on meiotic transcripts and induces nuclear exosome-mediated elimination. During meiosis, Mmi1 is sequestered by a chromosome-associated dot structure, Mei2 dot, allowing meiosis-specific transcripts to be stably expressed. Red1, a zinc-finger protein, is also known to participate in the Mmi1/DSR elimination system, although its molecular function has remained elusive. To uncover the detailed molecular mechanisms underlying the Mmi1/DSR elimination system, we sought to identify factors that interact genetically with Mmi1. Here, we show that one of the identified factors, Iss10, is involved in the Mmi1/DSR system by regulating the interaction between Mmi1 and Red1. In cells lacking Iss10, association of Red1 with Mmi1 is severely impaired, and target transcripts of Mmi1 are ectopically expressed in the mitotic cycle. During meiosis, Iss10 is downregulated, resulting in dissociation of Red1 from Mmi1 and subsequent suppression of Mmi1 activity.
    Full-text · Article · Aug 2013 · Nucleic Acids Research
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    • "One is the nutrient (glucose) signaling pathway [18] and the other is the mating pathway. This mating pathway closely resembles the mitogen-activated protein kinase (MAPK) pathway in mammalian cells [19, 20]. A fission yeast cell usually divides by mitosis in rich medium. "
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    ABSTRACT: G protein-coupled receptors (GPCRs) are associated with a great variety of biological activities. Yeasts are often utilized as a host for heterologous GPCR assay. We engineered the intense reporter plasmids for fission yeast to produce green fluorescent protein (GFP) through its endogenous GPCR pathway. As a control region of GFP expression on the reporter plasmid, we focused on seven endogenous genes specifically activated through the pathway. When upstream regions of these genes were used as an inducible promoter in combination with LPI terminator, the mam2 upstream region produced GFP most rapidly and intensely despite the high background. Subsequently, LPI terminator was replaced with the corresponding downstream regions. The SPBC4.01 downstream region enhanced the response with the low background. Furthermore, combining SPBC4.01 downstream region with the sxa2 upstream region, the signal to noise ratio was obviously better than those of other regions. We also evaluated the time- and dose-dependent GFP productions of the strains transformed with the reporter plasmids. Finally, we exhibited a model of simplified GPCR assay with the reporter plasmid by expressing endogenous GPCR under the control of the foreign promoter.
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