title: Cln3 blocks IME1 transcription and the Ime1-Ume6 interaction to cause the sporulation incompetence in a sake yeast, Kyokai no. 7.
abstract: Industrial yeasts, including a sake yeast Kyokai no. 7 (K7), are generally unable to sporulate. In K7 (Saccharomyces cerevisiae) cells, IME1 transcription was not induced under sporulation conditions, and K7 cells partially restored sporulation ability when transformed with a multicopy plasmid bearing IME1. However, the mechanisms of sporulation incompetence in industrial yeasts are poorly understood. We demonstrated that the deletion of the G1 cyclin CLN3, a key activator of the cell cycle, allows K7 cells to induce IME1 transcription and sporulate under sporulation conditions. In K7 cells, CLN3 mRNA and protein were not down-regulated despite sporulation conditions. Moreover, using a two-hybrid assay, we found that Ime1-Ume6 interaction was promoted in Cln3-deficient K7 cells. Thus, Cln3 is involved in the mechanism underlying sporulation incompetence by inhibiting IME1 transcription and the Ime1-Ume6 interaction. Based on these findings, we hypothesize that the absence of transmission of nutrient starvation signals to CLN3 leads to sporulation incompetence in K7 cells.
authors.affiliation: Department of Biotechnology, Faculty of Bioresource Science, Akita Prefectural University, 241-438 Kaidoubata-Nishi, Shimoshinjyo-Nakano, Akita-shi, Akita Prefecture 010-0195, Japan. nnakazawa@akita-pu.ac.jp
authors.forename: Nobushige
authors.initials: N
authors.lastname: Nakazawa
authors.forename: Kimio
authors.initials: K
authors.lastname: Abe
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Koshika
authors.forename: Kimio
authors.initials: K
authors.lastname: Iwano
mesh_terms: D016213:Cyclins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D007218:Industrial Microbiology; D008540:Meiosis / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D013172:Spores, Fungal / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: C079895:CLN3 protein, S cerevisiae; D016213:Cyclins; C080326:IME1 protein, S cerevisiae; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C089979:UME6 protein, S cerevisiae