Dai Hirata

Publications (32)181.66 Total impact

• Article: Fission Yeast Leucine-Rich Repeat Protein Lrp1 Is Essential for Cell Morphogenesis as a Component of the Morphogenesis Orb6 Network (MOR).

  Kazunori Kume, Shunsuke Kubota, Takayuki Koyano, Muneyoshi Kanai, Masaki Mizunuma, Takashi Toda, Dai Hirata
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  ABSTRACT: In eukaryotes, cell morphogenesis is regulated coordinately with the cell cycle. In fission yeast, the morphogenesis network MOR (morphogenesis Orb6 network) consists of 5 conserved proteins, Pmo25, Nak1, Mor2, Orb6, and Mob2, and is essential for cell polarity control and cell separation following cytokinesis. Here we show that the conserved leucine-rich repeat protein Lrp1 is required for cell morphogenesis as a newly recognized component of MOR. Lrp1 has 4 leucine-rich repeats in its N-terminus and is a homolog of the budding yeast Sog2, which is a component of the RAM network (regulation of Ace2 activity and cellular morphogenesis). Lrp1 was essential for both cell growth and cell morphogenesis as were the other MOR components. Lrp1 was localized to the SPBs (spindle pole bodies, the yeast equivalent of the animal centrosome) throughout the cell cycle and to the medial ring during cytokinesis. Lrp1 interacted with Nak1 and was important for Orb6 kinase activity. Thus Lrp1 proved to function upstream of Orb6 in cell morphogenesis.
  Bioscience Biotechnology and Biochemistry 05/2013; · 1.28 Impact Factor
• Article: cAMP/PKA Regulates Multiple Aspects of Cellular Events by Phosphorylating Whi3 Cell-Cycle Regulator in Budding Yeast.

  Masaki Mizunuma, Ryohei Tsubakiyama, Takafumi Ogawa, Atsunori Shitamukai, Yoshifumi Kobayashi, Tomomi Inai, Kazunori Kume, Dai Hirata
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  ABSTRACT: The Start/G1 phase in the cell cycle is an important period during which cells determine the fate, onset of mitotic progression or the switch to developmental stages in response to both external and internal signals. In the budding yeast Saccharomyces cerevisiae, Whi3, a negative regulator of the G1 cyclins, has been identified as a positive regulator of cell-size control and is involved in the regulation of Start. However, the regulatory pathway of Whi3 governing the response to multiple signals remains largely unknown. Here we show that Whi3 was phosphorylated by the RAS/cAMP-dependent protein kinase (PKA) and that the phosphorylation of Ser-568 in Whi3 by PKA played an inhibitory role in the Whi3 function. Phosphorylation of Whi3 by PKA led to decreased interaction of it with CLN3 G1 cyclin mRNA and was required for the promotion of the G1/S progression. Further, we demonstrate that the phospho-mimetic S568D mutation of Whi3 prevented the developmental fate switch to sporulation or invasive growth. Thus, PKA modulated the function of Whi3 by phosphorylation, thus implicating PKA-mediated modulation of Whi3 in multiple cellular events.
  Journal of Biological Chemistry 03/2013; · 4.77 Impact Factor
• Article: Analysis of free fatty acids in sake by an enzymatic method and its application for estimating ethyl caproate and selecting yeast with high productivity of the ester.

  Takashi Kuribayashi, Mitsuoki Kaneoke, Dai Hirata, Ken-ichi Watanabe
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  ABSTRACT: We show that the concentration of total free fatty acids (FFAs) in sake produced by yeast with high productivity of ethyl caproate could be approximated by the concentration of 2 FFAs, caproic and caprylic acids. Measurement of the total FFAs concentration by an enzymatic method proved useful for both estimating the ethyl caproate concentration in sake and also for yeast breeding.
  Bioscience Biotechnology and Biochemistry 02/2012; 76(2):391-4. · 1.28 Impact Factor
• Article: Systematic localization study on novel proteins encoded by meiotically up-regulated ORFs in fission yeast.

  Chiho Ikebe, Manabu Konishi, Dai Hirata, Takahiro Matsusaka, Takashi Toda
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  ABSTRACT: We conducted a mitotic localization study on gene products encoded by 56 uncharacterized fission yeast ORFs that were transcriptionally up-regulated during meiotic division. Despite meiotic gene induction, these genes were expressed during mitosis as well. Seven gene products were localized in the nucleus and/or chromatin; another one was a mitosis-specific spindle pole body component and, intriguingly, its human homologue was also localized in the centrosome of cultured HeLa cells. Two products appeared to be localized in cytoplasmic microtubules, whereas four were mitochondrial proteins. Three other proteins were found in the medial ring upon cytokinesis and another was localized on the entire cell periphery. The remaining 38 proteins were detected in the cytoplasm and showed varied spatial patterns. This systematic study helps our integrated understanding of all the protein functions in the fission yeast as a eukaryotic model.
  Bioscience Biotechnology and Biochemistry 12/2011; 75(12):2364-70. · 1.28 Impact Factor
• Article: Analysis of the biological activity of a novel 24-membered macrolide JBIR-19 in Saccharomyces cerevisiae by the morphological imaging program CalMorph.

  Shinsuke Ohnuki, Tomohide Kobayashi, Hayato Ogawa, Ikuko Kozone, Jun-Ya Ueda, Motoki Takagi, Kazuo Shin-Ya, Dai Hirata, Satoru Nogami, Yoshikazu Ohya
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  ABSTRACT: To investigate the biological activity of a novel 24-membered macrolide compound, JBIR-19, isolated from the culture broth of the entomopathogenic fungus Metarhizium sp. fE61, morphological changes in yeast cells were examined using the automated image-processing program CalMorph. Principal components analysis was used to elucidate dynamic changes in the phenotypes, revealing two independent effects of JBIR-19 in yeast cells: bud elongation and increased size of the actin region. Using a fitness assay, we identified the genes required for robust growth in the presence of JBIR-19. Among these were CCW12, YLR111W, and DHH1, which are also involved in abnormal bud morphology. Based on these results and others, we predict intracellular targets of JBIR-19 and its functional interactions.
  FEMS Yeast Research 11/2011; 12(3):293-304. · 2.40 Impact Factor
• Article: Implication of Ca2+ in the regulation of replicative life span of budding yeast.

  Ryohei Tsubakiyama, Masaki Mizunuma, Anri Gengyo, Josuke Yamamoto, Kazunori Kume, Tokichi Miyakawa, Dai Hirata
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  ABSTRACT: In eukaryotic cells, Ca(2+)-triggered signaling pathways are used to regulate a wide variety of cellular processes. Calcineurin, a highly conserved Ca(2+)/calmodulin-dependent protein phosphatase, plays key roles in the regulation of diverse biological processes in organisms ranging from yeast to humans. We isolated a mutant of the SIR3 gene, implicated in the regulation of life span, as a suppressor of the Ca(2+) sensitivity of zds1Δ cells in the budding yeast Saccharomyces cerevisiae. Therefore, we investigated a relationship between Ca(2+) signaling and life span in yeast. Here we show that Ca(2+) affected the replicative life span (RLS) of yeast. Increased external and intracellular Ca(2+) levels caused a reduction in their RLS. Consistently, the increase in calcineurin activity by either the zds1 deletion or the constitutively activated calcineurin reduced RLS. Indeed, the shortened RLS of zds1Δ cells was suppressed by the calcineurin deletion. Further, the calcineurin deletion per se promoted aging without impairing the gene silencing typically observed in short-lived sir mutants, indicating that calcineurin plays an important role in a regulation of RLS even under normal growth condition. Thus, our results indicate that Ca(2+) homeostasis/Ca(2+) signaling are required to regulate longevity in budding yeast.
  Journal of Biological Chemistry 06/2011; 286(33):28681-7. · 4.77 Impact Factor
• Article: Implication of Ca2+ in the regulation of replicative lifespan of budding yeast

  Ryohei Tsubakiyama, Masaki Mizunuma, Anri Gengyo, Josuke Yamamoto, Kazunori Kume, Tokichi Miyakawa, Dai Hirata
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  ABSTRACT: In eukaryotic cells, calcium (Ca2+)-triggered signaling pathways are used to regulate a wide variety of cellular processes. Calcineurin, a highly conserved Ca2+/calmodulin (CaM)-dependent protein phosphatase, plays key roles in the regulation of diverse biological processes in organisms ranging from yeast to humans. We isolated a mutant of the SIR3 gene, implicated in the regulation of lifespan, as a suppressor of the Ca2+ sensitivity of zds1Δ cells in the budding yeast Saccharomyces cerevisiae. Therefore, we investigated a relationship between Ca2+-signaling and lifespan in yeast. Here we show that Ca2+ affected the replicative lifespan (RLS) of yeast. Increased external and intracellular Ca2+ levels caused a reduction in their RLS. Consistently, the increase in calcineurin activity by either the zds1 deletion or the constitutively activated calcineurin reduced RLS. Indeed, the shortened RLS of zds1Δ cells was suppressed by the calcineurin deletion. Further, the calcineurin deletion per se promoted ageing without impairing the gene silencing typically observed in short-lived sir mutants, indicating that calcineurin plays an important role in a regulation of RLS even under normal growth condition. Thus, our results indicate that Ca2+ homeostasis/Ca2+-signaling is required to regulate longevity in budding yeast.
  Journal of Biological Chemistry 06/2011; · 4.77 Impact Factor
• Article: Calcineurin ensures a link between the DNA replication checkpoint and microtubule-dependent polarized growth.

  Kazunori Kume, Takayuki Koyano, Muneyoshi Kanai, Takashi Toda, Dai Hirata
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  ABSTRACT: Microtubules are central to eukaryotic cell morphogenesis. Microtubule plus-end tracking proteins (+TIPs) transport polarity factors to the cell cortex, thereby playing a key role in both microtubule dynamics and cell polarity. However, the signalling pathway linking +TIPs to cell polarity control remains elusive. Here we show that the fission yeast checkpoint kinase Cds1 (Chk2 homologue) delays the transition of growth polarity from monopolar to bipolar (termed NETO; new-end take-off). The +TIPs CLIP170 homologue Tip1 and kinesin Tea2 are responsible for this delay, which is accompanied by a reduction in microtubule dynamics at the cell tip. Remarkably, microtubule stabilization occurs asymmetrically, prominently at the non-growing cell end, which induces abnormal accumulation of the polarity factor Tea1. Importantly, NETO delay requires activation of calcineurin, which is carried out by Cds1, resulting in Tip1 dephosphorylation. Thus, our study establishes a critical link between calcineurin and checkpoint-dependent cell morphogenesis.
  Nature Cell Biology 02/2011; 13(3):234-42. · 19.49 Impact Factor
• Article: Sake lees fermented with lactic acid bacteria prevents allergic rhinitis-like symptoms and IgE-mediated basophil degranulation.

  Seiji Kawamoto, Mitsuoki Kaneoke, Kayo Ohkouchi, Yuichi Amano, Yuki Takaoka, Kazunori Kume, Tsunehiro Aki, Susumu Yamashita, Ken-ichi Watanabe, Motoni Kadowaki, Dai Hirata, Kazuhisa Ono
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  ABSTRACT: We tested the effect of oral administration of fermented sake lees with lactic acid bacteria (FESLAB) on a murine model of allergic rhinitis upon immunization and nasal sensitization with ovalbumin (OVA). We used Lactobacillus paracasei NPSRIk-4 (isolated from sake lees), and L. brevis NPSRIv-8 (from fermented milk) as starter strains to produce the FESLAB. Oral FESLAB administration resulted in the development of significantly fewer sneezing symptoms than those seen in sham control animals given sterile water. We also found that FESLAB suppressed the allergen-induced degranulation of RBL2H3 rat basophilic leukemia cells.
  Bioscience Biotechnology and Biochemistry 01/2011; 75(1):140-4. · 1.28 Impact Factor
• Article: Fission yeast germinal center (GC) kinase Ppk11 interacts with Pmo25 and plays an auxiliary role in concert with the morphogenesis Orb6 network (MOR) in cell morphogenesis.

  Tetsuya Goshima, Kazunori Kume, Takayuki Koyano, Yoshikazu Ohya, Takashi Toda, Dai Hirata
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  ABSTRACT: How cell morphology and the cell cycle are coordinately regulated is a fundamental subject in cell biology. In fission yeast, 2 germinal center kinases (GCKs), Sid1 and Nak1, play an essential role in septation/cytokinesis and cell separation/cell polarity control, respectively, as components of the septation initiation network (SIN) and the morphogenesis Orb6 network (MOR). Here we show that a third GCK, Ppk11, is also required for efficient cell separation particularly, at a high temperature. Although Ppk11 is not essential for cell division, this kinase plays an auxiliary role in concert with MOR in cell morphogenesis. Ppk11 physically interacts with the MOR component Pmo25 and is localized to the septum, by which Ppk11 is crucial for Pmo25 targeting/accumulation to the septum. The conserved C-terminal WDF motif of Ppk11 is essential for both septum accumulation of Pmo25 and efficient cell separation. In contrast its kinase activity is required only for cell separation. Thus, both interaction of Ppk11 with Pmo25 and Ppk11 kinase activity are critical for efficient cell separation.
  Journal of Biological Chemistry 11/2010; 285(45):35196-205. · 4.77 Impact Factor
• Source

  Available from: Dannel Mccollum

  Article: The mitosis-to-interphase transition is coordinated by cross talk between the SIN and MOR pathways in Schizosaccharomyces pombe.

  Samriddha Ray, Kazunori Kume, Sneha Gupta, Wanzhong Ge, Mohan Balasubramanian, Dai Hirata, Dannel McCollum
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  ABSTRACT: The mechanisms that regulate cytoskeletal remodeling during the transition between mitosis and interphase are poorly understood. In fission yeast the MOR pathway promotes actin polarization to cell tips in interphase, whereas the SIN signaling pathway drives actomyosin ring assembly and cytokinesis. We show that the SIN inhibits MOR signaling in mitosis by interfering with Nak1 kinase-mediated activation of the most downstream MOR component, the NDR family kinase Orb6. Inactivation of the MOR may be a key function of the SIN because attenuation of MOR signaling rescued the cytokinetic defects of SIN mutants and allowed weak SIN signaling to trigger ectopic cytokinesis. Furthermore, failure to inhibit the MOR is toxic when the cell division apparatus is compromised. Together, our results reveal a mutually antagonistic relationship between the SIN and MOR pathways, which is important for completion of cytokinesis and coordination of cytoskeletal remodeling at the mitosis-to-interphase transition.
  The Journal of Cell Biology 09/2010; 190(5):793-805. · 10.26 Impact Factor
• Article: Search for kinases related to transition of growth polarity in fission yeast.

  Takayuki Koyano, Kazunori Kume, Manabu Konishi, Takashi Toda, Dai Hirata
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  ABSTRACT: In eukaryotes, cell polarity is essential for cell proliferation, differentiation, and development. It is regulated in 3 steps: establishment, maintenance, and transition. Compared to current knowledge of establishment and maintenance, the mechanism regulating the transition of cell polarity is poorly understood. In fission yeast during the G2 phase, growth polarity undergoes a dramatic transition, from monopolar to bipolar growth (termed NETO: new end take off). In this study, we screened systematically for protein kinases related to NETO using a genome-wide kinase deletion library. Analysis of these deletions suggested that 35 and 2 kinases had a putative positive and a negative role, respectively, in NETO. Moreover, 5 kinases were required for NETO-delay in the G1-arrested cdc10 mutant. These results suggest that many signaling pathways are involved in the regulation of NETO.
  Bioscience Biotechnology and Biochemistry 01/2010; 74(5):1129-33. · 1.28 Impact Factor
• Article: Identification of Tup1 and Cyc8 mutations defective in the responses to osmotic stress.

  Yoshifumi Kobayashi, Tomomi Inai, Masaki Mizunuma, Ichitaro Okada, Atsunori Shitamukai, Dai Hirata, Tokichi Miyakawa
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  ABSTRACT: In the yeast Saccharomyces cerevisiae, Tup1, in association with Cyc8 (Ssn6), functions as a general transcriptional corepressor. This repression is mediated by recruitment of the Tup1-Cyc8 complex to target promoters through sequence-specific DNA-binding proteins such as Sko1, which mediates the HOG pathway-dependent regulation. We identified tup1 and cyc8 mutant alleles as the suppressor of osmo-sensitivity of the hog1Delta strain. In these mutants, although the expression of the genes under the control of DNA-binding proteins other than Sko1 was apparently normal, the Sko1-regulated genes GRE2 and AHP1 were derepressed under non-stress conditions, suggesting that the Tup1 and Cyc8 mutant proteins were specifically defective in the repression of the Sko1-dependent genes. Chromatin immunoprecipitation analyses of the GRE2 promoter in the mutants demonstrated that the Sko1-Tup1-Cyc8 complex was localized to the promoter, together with Gcn5/SAGA, suggesting that the erroneous recruitment of SAGA to the promoter led to the derepression.
  Biochemical and Biophysical Research Communications 04/2008; 368(1):50-5. · 2.48 Impact Factor
• Article: Diversity of Ca2+-induced morphology revealed by morphological phenotyping of Ca2+-sensitive mutants of Saccharomyces cerevisiae.

  Shinsuke Ohnuki, Satoru Nogami, Hanako Kanai, Dai Hirata, Yoichiro Nakatani, Shinichi Morishita, Yoshikazu Ohya
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  ABSTRACT: Yeast cell morphology can be treated as a quantitative trait using the image processing software CalMorph. In the present study, we investigated Ca(2+)-induced morphological changes in Ca(2+)-sensitive (cls) mutants of Saccharomyces cerevisiae, based on the discovery that the characteristic Ca(2+)-induced morphological changes in the Ca(2+)-sensitive mutant zds1 reflect changes in the Ca(2+) signaling-mediated cell cycle control pathway. By applying hierarchical cluster analysis to the quantitative morphological data of 58 cls mutants, 31 of these mutants were classified into seven classes based on morphological similarities. The patterns of morphological change induced by Ca(2+) in one class differed from those of another class. Based on the results obtained using versatile methods for phenotypic analysis, we conclude that a high concentration of Ca(2+) exerts a wide variety of effects on yeast and that there are multiple Ca(2+)-regulatory pathways that are distinct from the Zds1p-related pathway.
  Eukaryotic Cell 06/2007; 6(5):817-30. · 3.60 Impact Factor
• Article: A method for Pmo25-associated kinase assay in fission yeast: the activity is dependent on two gC kinases Nak1 and Sid1.

  Kazunori Kume, Tetsuya Goshima, Kohji Miyahara, Takashi Toda, Dai Hirata
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  ABSTRACT: In fission yeast, the conserved proteins, MO25/Pmo25, GC kinase/Nak1, Furry/Mor2, NDR kinase/Orb6, and Mob2, constitute the morphogenesis Orb6 network (MOR). Previously we showed that Pmo25 functions as an upstream component of MOR and that it plays a connecting role between the septation initiation network (SIN) and MOR. Here we establish a Pmo25-associated kinase assay and show that the activity is dependent on Nak1/MOR and Sid1/SIN.
  Bioscience Biotechnology and Biochemistry 03/2007; 71(2):615-7. · 1.28 Impact Factor
• Source

  Available from: ncbi.nlm.nih.gov

  Article: Involvement of calcineurin-dependent degradation of Yap1p in Ca2+-induced G2 cell-cycle regulation in Saccharomyces cerevisiae.

  Hiroshi Yokoyama, Masaki Mizunuma, Michiyo Okamoto, Josuke Yamamoto, Dai Hirata, Tokichi Miyakawa
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  ABSTRACT: The Ca2+-activated pathways in Saccharomyces cerevisiae induce a delay in the onset of mitosis through the activation of Swe1p, a negative regulatory kinase that inhibits the Cdc28p/Clb complex. We isolated the YAP1 gene as a multicopy suppressor of calcium sensitivity owing to the loss of ZDS1, a negative regulator of SWE1 and CLN2 gene expression. YAP1 deletion on a zds1delta background exacerbated the Ca2+-related phenotype. Yap1p was degraded in a calcineurin-dependent manner when cells were exposed to calcium. In yap1delta cells, the expression level of the RPN4 gene encoding a transcription factor for the subunits of the ubiquitin-proteasome system was diminished. The deletion of YAP1 gene or RPN4 gene led to the accumulation of Swe1p and Cln2p. Yap1p was a substrate of calcineurin in vivo and in vitro. The calcineurin-mediated Yap1p degradation seems to be a long adaptive response that assures a G2 delay in response to a stress that causes the activation of the calcium signalling pathways.
  EMBO Reports 06/2006; 7(5):519-24. · 7.36 Impact Factor
• Source

  Available from: tut.fi

  Article: Evaluation of image processing programs for accurate measurement of budding and fission yeast morphology.

  Genjiro Suzuki, Hiroshi Sawai, Miwaka Ohtani, Satoru Nogami, Fumi Sano-Kumagai, Ayaka Saka, Masashi Yukawa, Taro L Saito, Jun Sese, Dai Hirata, Shinichi Morishita, Yoshikazu Ohya
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  ABSTRACT: To study the cellular functions of gene products, various yeast morphological mutants have been investigated. To describe yeast morphology objectively, we have developed image processing programs for budding and fission yeast. The programs, named CalMorph for budding yeast and F-CalMorph for fission yeast, directly process microscopic images and generate quantitative data about yeast cell shape, nuclear shape and location, and actin distribution. Using CalMorph, we can easily and quickly obtain various quantitative data reproducibly. To study the utility and reliability of CalMorph, we evaluated its data in three ways: (1) The programs extracted three-dimensional bud information from two-dimensional digital images with a low error rate (<1%). (2) The absolute values of the diameters of manufactured fluorescent beads calculated with CalMorph were very close to those given in the manufacturer's data sheet. (3) The programs generated reproducible data consistent with that obtained by hand. Based on these results, we determined that CalMorph could monitor yeast morphological changes accompanied by the progression of the cell cycle. We discuss the potential of the CalMorph series as a novel tool for the analysis of yeast cell morphology.
  Current Genetics 04/2006; 49(4):237-47. · 2.56 Impact Factor
• Article: The V260I mutation in fission yeast alpha-tubulin Atb2 affects microtubule dynamics and EB1-Mal3 localization and activates the Bub1 branch of the spindle checkpoint.

  Kazuhide Asakawa, Kazunori Kume, Muneyoshi Kanai, Tetsuya Goshima, Kohji Miyahara, Susheela Dhut, Wee Wei Tee, Dai Hirata, Takashi Toda
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  ABSTRACT: We have identified a novel temperature-sensitive mutant of fission yeast alpha-tubulin Atb2 (atb2-983) that contains a single amino acid substitution (V260I). Atb2-983 is incorporated into the microtubules, and their overall structures are not altered noticeably, but microtubule dynamics is compromised during interphase. atb2-983 displays a high rate of chromosome missegregation and is synthetically lethal with deletions in a subset of spindle checkpoint genes including bub1, bub3, and mph1, but not with mad1, mad2, and mad3. During early mitosis in this mutant, Bub1, but not Mad2, remains for a prolonged period in the kinetochores that are situated in proximity to one of the two SPBs (spindle pole bodies). High dosage mal3(+), encoding EB1 homologue, rescues atb2-983, suggesting that Mal3 function is compromised. Consistently, Mal3 localization and binding between Mal3 and Atb2-983 are impaired significantly, and a mal3 single mutant, such as atb2-983, displays prolonged Bub1 kinetochore localization. Furthermore in atb2-983 back-and-forth centromere oscillation during prometaphase is abolished. Intriguingly, this oscillation still occurs in the mal3 mutant, indicating that there is another defect independent of Mal3. These results show that microtubule dynamics is important for coordinated execution of mitotic events, in which Mal3 plays a vital role.
  Molecular Biology of the Cell 04/2006; 17(3):1421-35. · 4.94 Impact Factor
• Article: Mal3, the fission yeast EB1 homologue, cooperates with Bub1 spindle checkpoint to prevent monopolar attachment.

  Kazuhide Asakawa, Mika Toya, Masamitsu Sato, Muneyoshi Kanai, Kazunori Kume, Tetsuya Goshima, Miguel Angel Garcia, Dai Hirata, Takashi Toda
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  ABSTRACT: Bipolar microtubule attachment is central to genome stability. Here, we investigate the mitotic role of the fission yeast EB1 homologue Mal3. Mal3 shows dynamic inward movement along the spindle, initial emergence at the spindle pole body (SPB) and translocation towards the equatorial plane, followed by sudden disappearance. Deletion of Mal3 results in early mitotic delay, which is dependent on the Bub1, but not the Mad2, spindle checkpoint. Consistently, Bub1, but not Mad2, shows prolonged kinetochore localization. Double mutants between mal3 and a subset of checkpoint mutants, including bub1, bub3, mad3 and mph1, but not mad1 or mad2, show massive chromosome mis-segregation defects. In mal3bub1 mutants, both sister centromeres tend to remain in close proximity to one of the separating SPBs. Further analysis indicates that mis-segregated centromeres are exclusively associated with the mother SPB. Mal3, therefore, has a role in preventing monopolar attachment in cooperation with the Bub1/Bub3/Mad3/Mph1-dependent checkpoint.
  EMBO Reports 01/2006; 6(12):1194-200. · 7.36 Impact Factor
• Article: Implication of Pkc1p protein kinase C in sustaining Cln2p level and polarized bud growth in response to calcium signaling in Saccharomyces cerevisiae.

  Masaki Mizunuma, Dai Hirata, Tokichi Miyakawa
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  ABSTRACT: Protein kinase C, a highly conserved signaling molecule among eukaryotes, has been implicated in the regulation of cellular processes such as cell proliferation and polarized growth. In Saccharomyces cerevisiae, the unique protein kinase C Pkc1p is thought to have multiple functions, including the activation of the Mpk1p (Slt2p) MAP kinase pathway, which is essential for cell wall construction and bud emergence. However, little is known about the other functions of Pkc1p. In the course of screening for the mutants that suppress the Ca2+-sensitivity phenotype of the Ca2+-sensitive strain zdsDelta, we isolated a novel mutant allele (scz6/pkc1-834) of PKC1. Unlike the previously characterized PKC1 allele stt1-1, heat-shock-induced Mpk1p activation and cell-wall integrity were not impaired in the pkc1-834 mutant. By contrast, the mutant was defective in the maintenance of Ca2+-induced F-actin polarization in a manner independent of Mpk1p activation. This phenotype was caused by a decreased expression level of the G1 cyclin Cln2p. The Rho1 small G protein molecular switch was suggested to be involved in the novel Pkc1p function. The Pkc1p novel function was required for posttranscriptional upregulation of Cln2p and appeared to be important for the coordinated regulation of polar bud growth and the cell cycle.
  Journal of Cell Science 10/2005; 118(Pt 18):4219-29. · 6.11 Impact Factor