Novel Rho GTPase Involved in Cytokinesis and Cell Wall Integrity in the Fission Yeast
            <i>Schizosaccharomyces pombe</i>

Santos, Beatriz Tamargo; Gutiérrez, J.L.; Calonge, Teresa M.; Pérez, Pilar

doi:10.1128/ec.2.3.521-533.2003

Cited by 59 publications

(89 citation statements)

References 53 publications

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“…For example, our data showed that a general delay in cell separation caused by compromised functions of a wide range of proteins, including Ace2p, some of Ace2p's targets (Mid2p, Agn1p, and Eng1p), septins, exocyst component Sec8p, and small GTPase Rho4p, all allow SIN mutant cells to survive the stress imposed by a weak cell wall and septum (Table 3), probably because these mutations slow down or block the action of septum-degrading enzymes on the septum. In addition, we also found that the presence of sorbitol in the medium could rescue the cell lysis phenotype of some mutations in SIN pathway components ( Figure 3A), suggesting that SIN mutants might have septum defects, as sorbitol can act as an osmotic stabilizer and has been shown to rescue the cell lysis phenotype in mutants with a defective cell wall in both S. cerevisiae and S. pombe (Ribas et al 1991;Cid et al 1995;Santos et al 2003). Furthermore, overexpression of the Rho1p GTPase can also rescue the lysis phenotype of sid2-250.…”

Section: Discussionmentioning

confidence: 82%

“…One line of evidence came from our observation that the growth defect and the cell lysis defect can be rescued by addition of the sorbitol in the media ( Figure 3B). Sorbitol can act as an osmotic stabilizer and has been shown to rescue the cell lysis phenotype in mutants with a defective cell wall in both Saccharomyces cerevisiae and S. pombe (Ribas et al 1991;Cid et al 1995;Santos et al 2003). In addition, we also observed the phenotypic rescue of other mutations in SIN pathway components by the presence of sorbitol, such as sid4-A1, spg1-106, sid1-125, and mob1-1 (Figure 3B), suggesting that SIN mutants have septum defects that can be stabilized by sorbitol.…”

Section: Resultsmentioning

confidence: 99%

“…The expression of Eng1p and Agn1p, together with at least five other proteins required for cell separation during the last stages of the cell cycle, is transcriptionally regulated by the transcription factor Ace2p (Rustici et al 2004;Alonso-Nunez et al 2005). In addition, various other proteins have been directly or indirectly implicated in the process of cell separation in fission yeast, as several mutants affecting cell-cell separation have been isolated, including mutations in the forkhead transcription factor sep1 (Yoshida et al 1994;Longtine et al 1996;Toda et al 1996;Ribar et al 1997;Sugiura et al 1998;Jiang and Hallberg 2000;Le Goff et al 2001;Wang et al 2002;Berlin et al 2003;Nakano et al 2003;Santos et al 2003;Tasto et al 2003;An et al 2004;Dekker et al 2004;Alonso-Nunez et al 2005;Bahler 2005;Garcia et al 2005). It is unclear how all of these proteins promote cell separation, but the exocyst complex, along with Mid2p and septins, was recently shown to be required for targeting of enzymes involved in septum cleavage to the septum .…”

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confidence: 99%

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A Role for the Septation Initiation Network in Septum Assembly Revealed by Genetic Analysis of sid2-250 Suppressors

et al. 2006

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In the fission yeast Schizosaccharomyces pombe the septation initiation network (SIN) is required for stabilization of the actomyosin ring in late mitosis as well as for ring constriction and septum deposition. In a genetic screen for suppressors of the SIN mutant sid2-250, we isolated a mutation, ace2-35, in the transcription factor Ace2p. Both ace2D and ace2-35 show defects in cell separation, and both can rescue the growth defects of some SIN mutants at low restrictive temperatures, where the SIN single mutants lyse at the time of cytokinesis. By detailed analysis of the formation and constriction of the actomyosin ring and septum in the sid2-250 mutant at low restrictive temperatures, we show that the lysis phenotype of the sid2-250 mutant is likely due to a weak cell wall and septum combined with enzymatic activity of septumdegrading enzymes. Consistent with the recent findings that Ace2p controls transcription of genes involved in cell separation, we show that disruption of some of these genes can also rescue sid2-250 mutants. Consistent with SIN mutants having defects in septum formation, many SIN mutants can be rescued at the low restrictive temperature by the osmotic stabilizer sorbitol. The small GTPase Rho1 is known to promote cell wall formation, and we find that Rho1p expressed from a multi-copy plasmid can also rescue sid2-250 at the low restrictive temperature. Together these results suggest that the SIN has a role in promoting proper cell wall formation at the division septa.

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Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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A Role for the Septation Initiation Network in Septum Assembly Revealed by Genetic Analysis of sid2-250 Suppressors

et al. 2006

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“…By doing so, AnBud3, and by inference activated Rho4, may control additional steps beyond recruitment of SepA, such as maintenance of the CAR or coordination of septum deposition with ring constriction. (e.g., Nakano et al 2003;Santos et al 2003).…”

Section: Discussionmentioning

confidence: 99%

Regulation of Septum Formation by the Bud3–Rho4 GTPase Module inAspergillus nidulans

Justa-Schuch

Seiler

et al. 2010

Genetics

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The ability of fungi to generate polarized cells with a variety of shapes likely reflects precise temporal and spatial control over the formation of polarity axes. The bud site selection system of Saccharomyces cerevisiae represents the best-understood example of such a morphogenetic regulatory system. However, the extent to which this system is conserved in the highly polarized filamentous fungi remains unknown. Here, we describe the functional characterization and localization of the Aspergillus nidulans homolog of the axial bud site marker Bud3. Our results show that AnBud3 is not required for polarized hyphal growth per se, but is involved in septum formation. In particular, our genetic and biochemical evidence implicates AnBud3 as a guanine nucleotide exchange factor for the GTPase Rho4. Additional results suggest that the AnBud3-Rho4 module acts downstream of the septation initiation network to mediate recruitment of the formin SepA to the site of contractile actin ring assembly. Our observations provide new insight into the signaling pathways that regulate septum formation in filamentous fungi.

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“…Given that there are four other Rho proteins (Rho2-Rho5) (Hirata et al, 1998;Nakano et al, 2002;Nakano et al, 2003;Santos et al, 2003;Wang et al, 2003) and several biochemically uncharacterized GEFs (Iwaki et al, 2003), it will take considerable effort in the future to sort out the biochemical specificities, cellular roles, and regulation of each Rho-GEF. In an effort to begin characterizing these proteins, Iwaki and colleagues deleted and overproduced the genes encoding all of them in fission yeast cells (Iwaki et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Cell wall remodeling at the fission yeast cell division site requires the Rho-GEF Rgf3p

Morrell‐Falvey

Ren

Feoktistova

et al. 2005

Journal of Cell Science

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IntroductionCytokinesis is the final step of the cell cycle that results in the formation of two daughter cells from one. This process is regulated temporally and spatially such that the replicated and segregated chromosomes are evenly divided between daughter cells. The genetically tractable yeast Schizosaccharomyces pombe is an excellent organism for studying cytokinesis as it divides by medial fission following assembly and contraction of an actomyosin-based cleavage apparatus that directs placement and assembly of new membrane and cell wall materials (Balasubramanian et al., 2004;Krapp et al., 2004;Wolfe and Gould, 2005). Furthermore, numerous mutations are available that are defective in each step of the cell division process.The initial phase of cytokinesis involves establishing the division site at the center of a symmetrical cell. This process begins at the onset of mitosis when components of the actomyosin ring are recruited to the cell cortex immediately overlaying the nucleus (reviewed by Balasubramanian et al., 2004;Wolfe and Gould, 2005). The next steps of cytokinesis, actomyosin ring constriction and septation, require a conserved signaling cascade referred to as the septation initiation network (SIN) that is organized at the spindle pole body, a microtubuleorganizing center analogous to the mammalian centrosome (reviewed by Krapp et al., 2004;McCollum and Gould, 2001).Septation occurs concomitantly with actomyosin ring constriction as the primary septum is laid down in a centripetal manner behind the constricting CAR (reviewed by Le Goff et al., 1999a). Indeed, actomyosin ring constriction does not proceed in the absence of primary septum formation (Le Goff et al., 1999b;Liu et al., 1999). The primary septum consists primarily of unbranched 1,3-␤-glucan and 1,3-␣-glucan (Humbel et al., 2001) and Cps1p is a 1,3-␤-glucan synthase essential for its assembly (Le Goff et al., 1999b;Liu et al., 1999). , 2004). Efficient septum degradation and cell separation also require the exocyst complex, a MAPK (Pmk1p), a MAPK phosphatase (Pmp1p), calcineurin (Ppb1p), subunits of the mediator complex (Sep10p, Sep11p, and Sep15p), as well as septins and their regulator Mid2p (An et al., 2004;Hall and Russell, 2004;Sipiczki et al., 1993;Sugiura et al., 1998;Tasto et al., 2003;Toda et al., 1996;Wang et al., 2002;Yoshida et al., 1994). Precisely how these proteins are 5563Cytokinesis in Schizosaccharomyces pombe is accompanied by several stages of cell wall remodeling at the division site. Coincident with actomyosin ring constriction, primary and secondary septa are deposited and then the primary septum is degraded to release daughter cells from one another. These steps require the activities of glucan synthases and glucanases, respectively, which must be coordinated with one another to prevent cell lysis. The lad1-1 mutation undergoes cell lysis specifically at cell division owing to the absence of the Rgf3p Rho1-guanine nucleotide exchange factor (GEF) at the division site. Electron microscopic analysis indicates tha...

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Novel Rho GTPase Involved in Cytokinesis and Cell Wall Integrity in the Fission Yeast Schizosaccharomyces pombe

Cited by 59 publications

References 53 publications

A Role for the Septation Initiation Network in Septum Assembly Revealed by Genetic Analysis of sid2-250 Suppressors

A Role for the Septation Initiation Network in Septum Assembly Revealed by Genetic Analysis of sid2-250 Suppressors

Regulation of Septum Formation by the Bud3–Rho4 GTPase Module inAspergillus nidulans

Cell wall remodeling at the fission yeast cell division site requires the Rho-GEF Rgf3p

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