scholarly journals A septin-Hof1 scaffold at the yeast bud neck binds and organizes actin cables

2020 ◽  
Vol 31 (18) ◽  
pp. 1988-2001 ◽  
Author(s):  
Mikael V. Garabedian ◽  
Alison Wirshing ◽  
Anna Vakhrusheva ◽  
Bengi Turegun ◽  
Olga S. Sokolova ◽  
...  
Keyword(s):  
Mother Cell ◽  
Vesicle Transport ◽  
Cell Compartment ◽  
Bud Neck ◽  
Actin Cables

Septins and Hof1 form evenly spaced pillars at the yeast bud neck, which align, orient, and bundle actin cables entering the mother cell compartment to facilitate polarized vesicle transport.

scholarly journals Stable and Dynamic Axes of Polarity Use Distinct Formin Isoforms in Budding Yeast

2004 ◽  
Vol 15 (11) ◽  
pp. 4971-4989 ◽  
Author(s):  
David Pruyne ◽  
Lina Gao ◽  
Erfei Bi ◽  
Anthony Bretscher
Keyword(s):  
Mother Cell ◽  
Feedback Signal ◽  
Secretory Vesicles ◽  
Rho Proteins ◽  
Polarized Secretion ◽  
Bud Neck ◽  
Morphological Defects ◽  
Bud Growth ◽  
Actin Cables ◽  
Cytoskeletal Elements

Bud growth in yeast is guided by myosin-driven delivery of secretory vesicles from the mother cell to the bud. We find transport occurs along two sets of actin cables assembled by two formin isoforms. The Bnr1p formin assembles cables that radiate from the bud neck into the mother, providing a stable mother-bud axis. These cables also depend on septins at the neck and are required for efficient transport from the mother to the bud. The Bni1p formin assembles cables that line the bud cortex and target vesicles to varying locations in the bud. Loss of these cables results in morphological defects as vesicles accumulate at the neck. Assembly of these cables depends on continued polarized secretion, suggesting vesicular transport provides a positive feedback signal for Bni1p activation, possibly by rho-proteins. By coupling different formin isoforms to unique cortical landmarks, yeast uses common cytoskeletal elements to maintain stable and dynamic axes in the same cell.

scholarly journals Yeast Formins Bni1 and Bnr1 Utilize Different Modes of Cortical Interaction during the Assembly of Actin Cables

2007 ◽  
Vol 18 (5) ◽  
pp. 1826-1838 ◽  
Author(s):  
Shawnna M. Buttery ◽  
Satoshi Yoshida ◽  
David Pellman
Keyword(s):  
Mother Cell ◽  
Fluorescence Recovery After Photobleaching ◽  
Actin Assembly ◽  
Actin Cable ◽  
Bud Neck ◽  
Cable Assembly ◽  
Different Populations ◽  
Actin Cables ◽  
Assembly Activity

The budding yeast formins Bni1 and Bnr1 control the assembly of actin cables. These formins exhibit distinct patterns of localization and polymerize two different populations of cables: Bni1 in the bud and Bnr1 in the mother cell. We generated a functional Bni1-3GFP that improved the visualization of Bni1 in vivo at endogenous levels. Bni1 exists as speckles in the cytoplasm, some of which colocalize on actin cables. These Bni1 speckles display linear, retrograde-directed movements. Loss of polymerized actin or specifically actin cables abolished retrograde movement, and resulted in depletion of Bni1 speckles from the cytoplasm, with enhanced targeting of Bni1 to the bud tip. Mutations that impair the actin assembly activity of Bni1 abolished the movement of Bni1 speckles, even when actin cables were present. In contrast, Bnr1-GFP or 3GFP-Bnr1 did not detectably associate with actin cables and was not observed as cytoplasmic speckles. Finally, fluorescence recovery after photobleaching demonstrated that Bni1 was very dynamic, exchanging between polarized sites and the cytoplasm, whereas Bnr1 was confined to the bud neck and did not exchange with a cytoplasmic pool. In summary, our results indicate that formins can have distinct modes of cortical interaction during actin cable assembly.

scholarly journals Assembly of Multiple CotC Forms into the Bacillus subtilis Spore Coat

2004 ◽  
Vol 186 (4) ◽  
pp. 1129-1135 ◽  
Author(s):  
Rachele Isticato ◽  
Giovanni Esposito ◽  
Rita Zilhão ◽  
Sofia Nolasco ◽  
Giuseppina Cangiano ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Posttranslational Modifications ◽  
Mother Cell ◽  
Spore Coat ◽  
Spore Surface ◽  
Subtilis Spore ◽  
Cell Compartment ◽  
Bacillus Subtilis Spore ◽  
Molecular Masses

ABSTRACT We report evidence that the CotC polypeptide, a previously identified component of the Bacillus subtilis spore coat, is assembled into at least four distinct forms. Two of these, having molecular masses of 12 and 21 kDa, appeared 8 h after the onset of sporulation and were probably assembled on the forming spore immediately after their synthesis, since no accumulation of either of them was detected in the mother cell compartment, where their synthesis occurs. The other two components, 12.5 and 30 kDa, were generated 2 h later and were probably the products of posttranslational modifications of the two early forms occurring directly on the coat surface during spore maturation. None of the CotC forms was found either on the spore coat or in the mother cell compartment of a cotH mutant. This indicates that CotH serves a dual role of stabilizing the early forms of CotC and promoting the assembly of both early and late forms on the spore surface.

scholarly journals Yeast formin Bni1p has multiple localization regions that function in polarized growth and spindle orientation

2012 ◽  
Vol 23 (3) ◽  
pp. 412-422 ◽  
Author(s):  
Wenyu Liu ◽  
Felipe H. Santiago-Tirado ◽  
Anthony Bretscher
Keyword(s):  
Coiled Coil ◽  
Binding Domain ◽  
Dominant Negative ◽  
Dominant Negative Effect ◽  
Spindle Orientation ◽  
Bud Neck ◽  
Negative Effect ◽  
The Right ◽  
Actin Cables ◽  
And Function

Formins are conserved proteins that assemble unbranched actin filaments in a regulated, localized manner. Budding yeast's two formins, Bni1p and Bnr1p, assemble actin cables necessary for polarized cell growth and organelle segregation. Here we define four regions in Bni1p that contribute to its localization to the bud and at the bud neck. The first (residues 1–333) requires dimerization for its localization and encompasses the Rho-binding domain. The second (residues 334–821) covers the Diaphanous inhibitory–dimerization–coiled coil domains, and the third is the Spa2p-binding domain. The fourth region encompasses the formin homology 1–formin homology 2–COOH region of the protein. These four regions can each localize to the bud cortex and bud neck at the right stage of the cell cycle independent of both F-actin and endogenous Bni1p. The first three regions contribute cumulatively to the proper localization of Bni1p, as revealed by the effects of progressive loss of these regions on the actin cytoskeleton and fidelity of spindle orientation. The fourth region contributes to the localization of Bni1p in tiny budded cells. Expression of mislocalized Bni1p constructs has a dominant-negative effect on both growth and nuclear segregation due to mislocalized actin assembly. These results define an unexpected complexity in the mechanism of formin localization and function.

scholarly journals The Yeast Formin Bnr1p Has Two Localization Regions That Show Spatially and Temporally Distinct Association with Septin Structures

2010 ◽  
Vol 21 (7) ◽  
pp. 1253-1262 ◽  
Author(s):  
Lina Gao ◽  
Wenyu Liu ◽  
Anthony Bretscher
Keyword(s):  
Cell Cycle ◽  
Cell Polarity ◽  
Actin Filaments ◽  
Full Length ◽  
Eukaryotic Proteins ◽  
Bud Neck ◽  
Temporal Localization ◽  
Actin Cables

Formins are conserved eukaryotic proteins that direct the nucleation and elongation of unbranched actin filaments. The yeast formins, Bni1p and Bnr1p, assemble actin cables from the bud cortex and bud neck, respectively, to guide overall cell polarity. Here we examine the regions of Bnr1p responsible for bud neck localization. We define two non-overlapping regions, Bnr1p-L1 (1-466) and Bnr1p-L2 (466-733), that can each localize to the bud neck independently of endogenous Bnr1p. Bnr1p-L1 and Bnr1p-L2 localize with septins at the bud neck, but show slightly differently spatial and temporal localization, reflecting the localization (Bnr1p-L1) or cell cycle timing (Bnr1p-L2) of full-length Bnr1p. Bnr1p is known to be very stably localized at the bud neck, and both Bnr1p-L1 and Bnr1p-L2 also show relatively stable localization there. Overexpression of Bnr1p-L1, but not Bnr1p-L2, disrupts septin organization at the bud neck. Thus Bnr1p has two separable regions that each contribute to its bud neck localization.

scholarly journals Cell Cycle-regulated Trafficking of Chs2 Controls Actomyosin Ring Stability during Cytokinesis

2005 ◽  
Vol 16 (5) ◽  
pp. 2529-2543 ◽  
Author(s):  
Lynn VerPlank ◽  
Rong Li
Keyword(s):  
Transmembrane Protein ◽  
Time Lapse ◽  
Mitotic Exit ◽  
Vesicle Transport ◽  
Myosin V ◽  
Contractile Ring ◽  
Mitotic Exit Network ◽  
Bud Neck ◽  
And Function ◽  
Ring Stability

Cytokinesis requires the coordination of many cellular complexes, particularly those involved in the constriction and reconstruction of the plasma membrane in the cleavage furrow. We have investigated the regulation and function of vesicle transport and fusion during cytokinesis in budding yeast. By using time-lapse confocal microscopy, we show that post-Golgi vesicles, as well as the exocyst, a complex required for the tethering and fusion of these vesicles, localize to the bud neck at a precise time just before spindle disassembly and actomyosin ring contraction. Using mutants affecting cyclin degradation and the mitotic exit network, we found that targeted secretion, in contrast to contractile ring activation, requires cyclin degradation but not the mitotic exit network. Analysis of cells in late anaphase bearing exocyst and myosin V mutations show that both vesicle transport and fusion machineries are required for the completion of cytokinesis, but this is not due to a delay in mitotic exit or assembly of the contractile ring. Further investigation of the dynamics of contractile rings in exocyst mutants shows these cells may be able to initiate contraction but often fail to complete the contraction due to premature disassembly during the contraction phase. This phenotype led us to identify Chs2, a transmembrane protein targeted to the bud neck through the exocytic pathway, as necessary for actomyosin ring stability during contraction. Chs2, as the chitin synthase that produces the primary septum, thus couples the assembly of the extracellular matrix with the dynamics of the contractile ring during cytokinesis.

scholarly journals The role of Myo2, a yeast class V myosin, in vesicular transport.

1995 ◽  
Vol 128 (6) ◽  
pp. 1055-1068 ◽  
Author(s):  
B Govindan ◽  
R Bowser ◽  
P Novick
Keyword(s):  
Mother Cell ◽  
Secretory Pathway ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Transit Times ◽  
Cargo Proteins ◽  
Section Electron ◽  
Synthetically Lethal ◽  
Actin Cables ◽  
Exocytic Pathway

Previous studies have shown that temperature-sensitive, myo2-66 yeast arrest as large, unbudded cells that accumulate vesicles within their cytoplasm (Johnston, G. C., J. A. Prendergast, and R. A. Singer. 1991. J. Cell Biol. 113:539-551). In this study we show that myo2-66 is synthetically lethal in combination with a subset of the late-acting sec mutations. Thin section electron microscopy shows that the post-Golgi blocked secretory mutants, sec1-1 and sec6-4, rapidly accumulate vesicles in the bud, upon brief incubations at the restrictive temperature. In contrast, myo2-66 cells accumulate vesicles predominantly in the mother cell. Double mutant analysis also places Myo2 function in a post-Golgi stage of the secretory pathway. Despite the accumulation of vesicles in myo2-66 cells, pulse-chase studies show that the transit times of several secreted proteins, including invertase and alpha factor, as well as the vacuolar proteins, carboxy-peptidase Y and alkaline phosphatase, are normal. Therefore the vesicles which accumulate in this mutant may function on an exocytic pathway that transports a set of cargo proteins that is distinct from those analyzed. Our observations are consistent with a role for Myo2 in transporting a class of secretory vesicles from the mother cell along actin cables into the bud.

scholarly journals LTE1 promotes exit from mitosis by multiple mechanisms

2016 ◽  
Vol 27 (25) ◽  
pp. 3991-4001 ◽  
Author(s):  
Jill E. Falk ◽  
Ian W. Campbell ◽  
Kelsey Joyce ◽  
Jenna Whalen ◽  
Anupama Seshan ◽  
...  
Keyword(s):  
Mother Cell ◽  
Regulatory Elements ◽  
Spindle Pole ◽  
Mitotic Exit ◽  
Genome Integrity ◽  
Cell Compartment ◽  
Activating Function ◽  
Spindle Pole Bodies ◽  
Mitotic Exit Network ◽  
Spindle Position

In budding yeast, alignment of the anaphase spindle along the mother–bud axis is crucial for maintaining genome integrity. If the anaphase spindle becomes misaligned in the mother cell compartment, cells arrest in anaphase because the mitotic exit network (MEN), an essential Ras-like GTPase signaling cascade, is inhibited by the spindle position checkpoint (SPoC). Distinct localization patterns of MEN and SPoC components mediate MEN inhibition. Most components of the MEN localize to spindle pole bodies. If the spindle becomes mispositioned in the mother cell compartment, cells arrest in anaphase due to inhibition of the MEN by the mother cell–restricted SPoC kinase Kin4. Here we show that a bud-localized activating signal is necessary for full MEN activation. We identify Lte1 as this signal and show that Lte1 activates the MEN in at least two ways. It inhibits small amounts of Kin4 that are present in the bud via its central domain. An additional MEN-activating function of Lte1 is mediated by its N- and C-terminal GEF domains, which, we propose, directly activate the MEN GTPase Tem1. We conclude that control of the MEN by spindle position is exerted by both negative and positive regulatory elements that control the pathway’s GTPase activity.

The “Pro” Sequence of the Sporulation-Specific ς Transcription Factor ςE Directs It to the Mother Cell Side of the Sporulation Septum

1999 ◽  
Vol 181 (19) ◽  
pp. 6171-6175 ◽  
Author(s):  
Jingliang Ju ◽  
W. G. Haldenwang
Keyword(s):  
Amino Acids ◽  
Transcription Factor ◽  
Bacillus Subtilis ◽  
Mother Cell ◽  
Fluorescent Protein ◽  
Amino Terminus ◽  
Cell Compartment ◽  
Intracellular Location ◽  
Specific Protease ◽  
Green Fluorescent

ABSTRACT ςE, a mother cell-specific transcription factor of sporulating Bacillus subtilis, is derived from an inactive precursor protein (pro-ςE). Activation of ςE occurs when a sporulation-specific protease (SpoIIGA) cleaves 27 amino acids from the pro-ςE amino terminus. This reaction is believed to take place at the mother cell-forespore septum. Using a chimera of pro-ςE and green fluorescent protein (GFP) to visualize the intracellular location of pro-ςE by fluorescence microscopy, and lysozyme treatment to separate the mother cell and forespore compartments, we determined that the pro-ςE::GFP signal, localized to the forespore septum prior to lysozyme treatment, is restricted to the mother cell compartment after treatment. Thus, pro-ςE::GFP had been sequestered to the mother cell side of the septum. This segregation of pro-ςE::GFP, and presumably pro-ςE, to the mother cell is likely to be the reason why ςE activity is restricted to that compartment.

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