scholarly journals The Checkpoint Kinase Hsl1p Is Activated by Elm1p-dependent Phosphorylation

2008 ◽  
Vol 19 (11) ◽  
pp. 4675-4686 ◽  
Author(s):  
Lee Szkotnicki ◽  
John M. Crutchley ◽  
Trevin R. Zyla ◽  
Elaine S.G. Bardes ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Stress Responses ◽  
Outdoor Environment ◽  
Checkpoint Kinase ◽  
Autoinhibitory Domain ◽  
Bud Emergence ◽  
Bud Neck ◽  
Mitotic Delay ◽  
Mitotic Inhibitor ◽  
Previous Identification

Saccharomyces cerevisiae cells growing in the outdoor environment must adapt to sudden changes in temperature and other variables. Many such changes trigger stress responses that delay bud emergence until the cells can adapt. In such circumstances, the morphogenesis checkpoint delays mitosis until a bud has been formed. Mitotic delay is due to the Wee1 family mitotic inhibitor Swe1p, whose degradation is linked to bud emergence by the checkpoint kinase Hsl1p. Hsl1p is concentrated at the mother-bud neck through association with septin filaments, and it was reported that Hsl1p activation involved relief of autoinhibition in response to septin interaction. Here we challenge the previous identification of an autoinhibitory domain and show instead that Hsl1p activation involves the phosphorylation of threonine 273, promoted by the septin-associated kinase Elm1p. We identified elm1 mutants in a screen for defects in Swe1p degradation and show that a phosphomimic T273E mutation in HSL1 bypasses the need for Elm1p in this pathway.

scholarly journals Sensing a bud in the yeast morphogenesis checkpoint: a role for Elm1

2016 ◽  
Vol 27 (11) ◽  
pp. 1764-1775 ◽  
Author(s):  
Hui Kang ◽  
Denis Tsygankov ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Division ◽  
Environmental Stresses ◽  
Bud Formation ◽  
Septin Ring ◽  
Bud Emergence ◽  
Bud Neck ◽  
Morphogenesis Checkpoint ◽  
Bud Site ◽  
Mitotic Inhibitor

Bud formation by Saccharomyces cerevisiae must be coordinated with the nuclear cycle to enable successful proliferation. Many environmental stresses temporarily disrupt bud formation, and in such circumstances, the morphogenesis checkpoint halts nuclear division until bud formation can resume. Bud emergence is essential for degradation of the mitotic inhibitor, Swe1. Swe1 is localized to the septin cytoskeleton at the bud neck by the Swe1-binding protein Hsl7. Neck localization of Swe1 is required for Swe1 degradation. Although septins form a ring at the presumptive bud site before bud emergence, Hsl7 is not recruited to the septins until after bud emergence, suggesting that septins and/or Hsl7 respond to a “bud sensor.” Here we show that recruitment of Hsl7 to the septin ring depends on a combination of two septin-binding kinases: Hsl1 and Elm1. We elucidate which domains of these kinases are needed and show that artificial targeting of those domains suffices to recruit Hsl7 to septin rings even in unbudded cells. Moreover, recruitment of Elm1 is responsive to bud emergence. Our findings suggest that Elm1 plays a key role in sensing bud emergence.

scholarly journals Bni5p, a Septin-Interacting Protein, Is Required for Normal Septin Function and Cytokinesis in Saccharomyces cerevisiae

2002 ◽  
Vol 22 (19) ◽  
pp. 6906-6920 ◽  
Author(s):  
Philip R. Lee ◽  
Sukgil Song ◽  
Hyeon-Su Ro ◽  
Chong J. Park ◽  
John Lippincott ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Localization ◽  
Growth Defect ◽  
Dependent Manner ◽  
Interacting Protein ◽  
Growth Defects ◽  
Bud Emergence ◽  
Bud Neck ◽  
And Function

ABSTRACT In the budding yeast Saccharomyces cerevisiae, the Cdc3p, Cdc10p, Cdc11p, Cdc12p, and Sep7p/Shs1p septins assemble early in the cell cycle in a ring that marks the future cytokinetic site. The septins appear to be major structural components of a set of filaments at the mother-bud neck and function as a scaffold for recruiting proteins involved in cytokinesis and other processes. We isolated a novel gene, BNI5, as a dosage suppressor of the cdc12-6 growth defect. Overexpression of BNI5 also suppressed the growth defects of cdc10-1, cdc11-6, and sep7Δ strains. Loss of BNI5 resulted in a cytokinesis defect, as evidenced by the formation of connected cells with shared cytoplasms, and deletion of BNI5 in a cdc3-6, cdc10-1, cdc11-6, cdc12-6, or sep7Δ mutant strain resulted in enhanced defects in septin localization and cytokinesis. Bni5p localizes to the mother-bud neck in a septin-dependent manner shortly after bud emergence and disappears from the neck approximately 2 to 3 min before spindle disassembly. Two-hybrid, in vitro binding, and protein-localization studies suggest that Bni5p interacts with the N-terminal domain of Cdc11p, which also appears to be sufficient for the localization of Cdc11p, its interaction with other septins, and other critical aspects of its function. Our data suggest that the Bni5p-septin interaction is important for septin ring stability and function, which is in turn critical for normal cytokinesis.

scholarly journals Involvement of an Actomyosin Contractile Ring in Saccharomyces cerevisiae Cytokinesis

1998 ◽  
Vol 142 (5) ◽  
pp. 1301-1312 ◽  
Author(s):  
Erfei Bi ◽  
Paul Maddox ◽  
Daniel J. Lew ◽  
E.D. Salmon ◽  
John N. McMillan ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Separation ◽  
Cortical Actin ◽  
Primary Defect ◽  
Septum Formation ◽  
Bud Emergence ◽  
Bud Neck ◽  
Bud Site ◽  
Type Ii Myosin

In Saccharomyces cerevisiae, the mother cell and bud are connected by a narrow neck. The mechanism by which this neck is closed during cytokinesis has been unclear. Here we report on the role of a contractile actomyosin ring in this process. Myo1p (the only type II myosin in S. cerevisiae) forms a ring at the presumptive bud site shortly before bud emergence. Myo1p ring formation depends on the septins but not on F-actin, and preexisting Myo1p rings are stable when F-actin is depolymerized. The Myo1p ring remains in the mother–bud neck until the end of anaphase, when a ring of F-actin forms in association with it. The actomyosin ring then contracts to a point and disappears. In the absence of F-actin, the Myo1p ring does not contract. After ring contraction, cortical actin patches congregate at the mother–bud neck, and septum formation and cell separation rapidly ensue. Strains deleted for MYO1 are viable; they fail to form the actin ring but show apparently normal congregation of actin patches at the neck. Some myo1Δ strains divide nearly as efficiently as wild type; other myo1Δ strains divide less efficiently, but it is unclear whether the primary defect is in cytokinesis, septum formation, or cell separation. Even cells lacking F-actin can divide, although in this case division is considerably delayed. Thus, the contractile actomyosin ring is not essential for cytokinesis in S. cerevisiae. In its absence, cytokinesis can still be completed by a process (possibly localized cell–wall synthesis leading to septum formation) that appears to require septin function and to be facilitated by F-actin.

scholarly journals Dynamics of septin ring and collar formation in Saccharomyces cerevisiae

2011 ◽  
Vol 392 (8-9) ◽  
pp. 689-697 ◽  
Author(s):  
Hsin Chen ◽  
Audrey S. Howell ◽  
Alex Robeson ◽  
Daniel J. Lew
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Septin Ring ◽  
Ring Assembly ◽  
Bud Emergence ◽  
Steady Rate ◽  
Constant Rate ◽  
Bud Neck ◽  
Quantitative Analyses ◽  
Reduced Rate ◽  
Mother Cells

Abstract Although the septin ring and collar in budding yeast were described over 20 years ago, there is still controversy regarding the organization of septin filaments within these structures and about the way in which the ring first forms and about how it converts into a collar at the mother-bud neck. Here we present quantitative analyses of the recruitment of fluorescently-tagged septins to the ring and collar through the cell cycle. Septin ring assembly began several minutes after polarity establishment and this interval was longer in daughter than in mother cells, suggesting asymmetric inheritance of septin regulators. Septins formed an initial faint and irregular ring, which became more regular as septins were recruited at a constant rate. This steady rate of septin recruitment continued for several minutes after the ring converted to a collar at bud emergence. We did not detect a stepwise change in septin fluorescence during the ring-to-collar transition. After collar formation, septins continued to accumulate at the bud neck, though at a reduced rate, until the onset of cytokinesis when the amount of neck-localized septins rapidly decreased. Implications for the mechanism of septin ring assembly are discussed.

Regulation of cytokinesis by the Elm1 protein kinase in Saccharomyces cerevisiae

2000 ◽  
Vol 113 (8) ◽  
pp. 1435-1445 ◽  
Author(s):  
N. Bouquin ◽  
Y. Barral ◽  
R. Courbeyrette ◽  
M. Blondel ◽  
M. Snyder ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Protein Kinase ◽  
Protein Kinases ◽  
Hyphal Growth ◽  
Negative Regulator ◽  
Bud Emergence ◽  
Bud Neck ◽  
Morphological Defects

A Saccharomyces cerevisiae mutant unable to grow in a cdc28-1N background was isolated and shown to be affected in the ELM1 gene. Elm1 is a protein kinase, thought to be a negative regulator of pseudo-hyphal growth. We show that Cdc11, one of the septins, is delocalised in the mutant, indicating that septin localisation is partly controlled by Elm1. Moreover, we show that cytokinesis is delayed in an elm1delta mutant. Elm1 levels peak at the end of the cell cycle and Elm1 is localised at the bud neck in a septin-dependent fashion from bud emergence until the completion of anaphase, at about the time of cell division. Genetic and biochemical evidence suggest that Elm1 and the three other septin-localised protein kinases, Hsl1, Gin4 and Kcc4, work in parallel pathways to regulate septin behaviour and cytokinesis. In addition, the elm1delta;) morphological defects can be suppressed by deletion of the SWE1 gene, but not the cytokinesis defect nor the septin mislocalisation. Our results indicate that cytokinesis in budding yeast is regulated by Elm1.

scholarly journals Identification of the bud emergence gene BEM4 and its interactions with rho-type GTPases in Saccharomyces cerevisiae.

1996 ◽  
Vol 16 (8) ◽  
pp. 4387-4395 ◽  
Author(s):  
D Mack ◽  
K Nishimura ◽  
B K Dennehey ◽  
T Arbogast ◽  
J Parkinson ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Synthetic Lethality ◽  
Cell Polarization ◽  
Growth Defect ◽  
Nucleotide Exchange ◽  
Loss Of Function ◽  
Multicopy Suppressor ◽  
Bud Emergence ◽  
Multicopy Suppressors ◽  
Multiple Copies

The Rho-type GTPase Cdc42p is required for cell polarization and bud emergence in Saccharomyces cerevisiae. To identify genes whose functions are linked to CDC42, we screened for (i) multicopy suppressors of a Ts- cdc42 mutant, (ii) mutants that require multiple copies of CDC42 for survival, and (iii) mutations that display synthetic lethality with a partial-loss-of-function allele of CDC24, which encodes a guanine nucleotide exchange factor for Cdc42p. In all three screens, we identified a new gene, BEM4. Cells from which BEM4 was deleted were inviable at 37 degrees C. These cells became unbudded, large, and round, consistent with a model in which Bem4p acts together with Cdc42p in polarity establishment and bud emergence. In some strains, the ability of CDC42 to serve as a multicopy suppressor of the Ts- growth defect of deltabem4 cells required co-overexpression of Rho1p, which is an essential Rho-type GTPase necessary for cell wall integrity. This finding suggests that Bem4p also affects Rho1p function. Bem4p displayed two-hybrid interactions with Cdc42p, Rho1p, and two of the three other known yeast Rho-type GTPases, suggesting that Bem4p can interact with multiple Rho-type GTPases. Models for the role of Bem4p include that it serves as a chaperone or modulates the interaction of these GTPases with one or more of their targets or regulators.

CDC55, a Saccharomyces cerevisiae gene involved in cellular morphogenesis: identification, characterization, and homology to the B subunit of mammalian type 2A protein phosphatase

1991 ◽  
Vol 11 (11) ◽  
pp. 5767-5780
Author(s):  
A M Healy ◽  
S Zolnierowicz ◽  
A E Stapleton ◽  
M Goebl ◽  
A A DePaoli-Roach ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Phosphatase ◽  
Protein A ◽  
Cdna Clones ◽  
Restrictive Temperature ◽  
B Subunit ◽  
Bud Emergence ◽  
New Gene ◽  
Cold Sensitive ◽  
Polymerase Chain

Microscopic screening of a collection of cold-sensitive mutants of Saccharomyces cerevisiae led to the identification of a new gene, CDC55, which appears to be involved in the morphogenetic events of the cell cycle. CDC55 maps between CDC43 and CHC1 on the left arm of chromosome VII. At restrictive temperature, the original cdc55 mutant produces abnormally elongated buds and displays a delay or partial block of septation and/or cell separation. A cdc55 deletion mutant displays a cold-sensitive phenotype like that of the original isolate. Sequencing of CDC55 revealed that it encodes a protein of about 60 kDa, as confirmed by Western immunoblots using Cdc55p-specific antibodies. This protein has greater than 50% sequence identity to the B subunits of rabbit skeletal muscle type 2A protein phosphatase; the latter sequences were obtained by analysis of peptides derived from the purified protein, a polymerase chain reaction product, and cDNA clones. An extragenic suppressor of the cdc55 mutation lies in BEM2, a gene previously identified on the basis of an apparent role in bud emergence.

scholarly journals Sec1p directly stimulates SNARE-mediated membrane fusion in vitro

2004 ◽  
Vol 167 (1) ◽  
pp. 75-85 ◽  
Author(s):  
Brenton L. Scott ◽  
Jeffrey S. Van Komen ◽  
Hassan Irshad ◽  
Song Liu ◽  
Kirilee A. Wilson ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Membrane Fusion ◽  
Membrane Trafficking ◽  
Snare Complex ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Bud Neck ◽  
Precise Role

Sec1 proteins are critical players in membrane trafficking, yet their precise role remains unknown. We have examined the role of Sec1p in the regulation of post-Golgi secretion in Saccharomyces cerevisiae. Indirect immunofluorescence shows that endogenous Sec1p is found primarily at the bud neck in newly budded cells and in patches broadly distributed within the plasma membrane in unbudded cells. Recombinant Sec1p binds strongly to the t-SNARE complex (Sso1p/Sec9c) as well as to the fully assembled ternary SNARE complex (Sso1p/Sec9c;Snc2p), but also binds weakly to free Sso1p. We used recombinant Sec1p to test Sec1p function using a well-characterized SNARE-mediated membrane fusion assay. The addition of Sec1p to a traditional in vitro fusion assay moderately stimulates fusion; however, when Sec1p is allowed to bind to SNAREs before reconstitution, significantly more Sec1p binding is detected and fusion is stimulated in a concentration-dependent manner. These data strongly argue that Sec1p directly stimulates SNARE-mediated membrane fusion.

Cytoplasmic Clb2 is required for timely inactivation of the mitotic inhibitor Swe1 and normal bud morphogenesis in Saccharomyces cerevisiae

2006 ◽  
Vol 51 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Jennifer K. Hood-DeGrenier ◽  
Cortney N. Boulton ◽  
Victoria Lyo
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mitotic Inhibitor
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