Cell and Molecular Biology of Septins

Fung, Karen; Dai, Lu; Trimble, William S.

doi:10.1016/b978-0-12-800180-6.00007-4

Cited by 111 publications

(139 citation statements)

References 200 publications

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“…After it was shown that Shs1 could occupy the same terminal position as Cdc11 in yeast septin hetero-octamers and confer different properties on the resulting complexes , it became apparent that, for mammalian septin complexes, placement of alternative subunits at different positions within hetero-octamers would likely provide a mechanism to impart differential features or functions appropriate to the septin structures in particular cell types or at particular stages in development (Saarikangas and Barral 2011;Mostowy and Cossart 2012;Sellin et al 2012;Fung et al 2014;Sellin et al 2014). Therefore, understanding how paralogous subunits, like Cdc11 and Shs1, have coevolved within the same complex and in the same cell type is of significant interest.…”

Section: Evidence For Heterotypic Octamer-octamer Interaction In Vivomentioning

confidence: 99%

“…The CTE of Cdc11 and Shs1 share a role critical for optimal septin function One feature conserved throughout the phylogeny of the septin protein family in opisthokont eukaryotes, from fungi to humans (Pan et al 2007;Nishihama et al 2011;Hall and Russell 2012;Fung et al 2014), is the presence of a long CTE appended to the globular Ras-related GTP-binding domain Weirich et al 2008). As first recognized in sequence comparisons of an Aspergillus nidulans septin (AspB) to other septin orthologs (Momany and Hamer 1997), the CTE always contains a segment of significant length wherein the spacing of overtly hydrophobic residues (and occasional polar residues whose arms are of sufficient length to have significant hydrophobicity) matches the 4-3 repeat characteristic of sequences able to form either homotypic or heterotypic coiled coils (Harbury et al 1995;Parry et al 2008).…”

Section: Assessment Of the Roles Of The A0 Helix And Its Basic Residumentioning

confidence: 99%

“…Detailed ultrastructural analysis led to the discovery that the septin complex that is the fundamental building block of the yeast filaments is a linear, hetero-octameric rod, with the order Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 (Bertin et al 2008), which polymerizes end-on-end via Cdc11-Cdc11 interaction. Subsequently, the nonpolar, linear hetero-octamer with twofold rotational symmetry was found to be characteristic of mammalian septin complexes too (Mostowy and Cossart 2012;Fung et al 2014). Each septin subunit comprises a Ras-related GTP-binding domain preceded by an N-terminal extension of variable length and followed by a C-terminal extension (CTE) of variable length Weirich et al 2008).…”

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Comprehensive Genetic Analysis of Paralogous Terminal Septin Subunits Shs1 and Cdc11 inSaccharomyces cerevisiae

et al. 2015

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Septins are a family of GTP-binding proteins considered to be cytoskeletal elements because they self-assemble into filaments and other higher-order structures in vivo. In budding yeast, septins establish a diffusion barrier at the bud neck between a mother and daughter cell, promote membrane curvature there, and serve as a scaffold to recruit other proteins to the site of cytokinesis. However, the mechanism by which any septin engages a partner protein has been unclear. The two most related and recently evolved subunits appear to be Cdc11 and Shs1, and the basic building blocks for assembling septin structures are hetero-octameric rods (Cdc11-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11 and Shs1-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Shs1). Loss of Cdc11 is not normally tolerated, whereas cells lacking Shs1 do not appear grossly abnormal. We established several different sensitized genetic backgrounds wherein Shs1 is indispensable, which allowed us to carry out the first comprehensive and detailed genetic analysis of Shs1 in vivo. Our analysis revealed several novel insights, including: (i) the sole portion of Shs1 essential for its function is a predicted coiled-coil-forming segment in its C-terminal extension (CTE); (ii) the CTE of Cdc11 shares this function; (iii) this role for the CTEs of Cdc11 and Shs1 is quite distinct from that of the CTEs of Cdc3 and Cdc12; and (iv) heterotypic Cdc11 and Shs1 junctions likely occur in vivo. KEYWORDS yeast; cytoskeleton; complexes; filaments; mutants S EPTINS are GTP-binding proteins conserved across Eukarya (except higher plants) (Pan et al. 2007;Nishihama et al. 2011). This protein family was first identified because the corresponding loci were among the temperature-sensitive (ts) cell division cycle (cdc) mutations isolated in Saccharomyces cerevisiae (Hartwell 1978). At the restrictive temperature, cdc3, cdc10, cdc11, and cdc12 mutants continued to bud, replicate, and segregate their chromosomes, yet failed to execute cell division, resulting in the formation of chains of multinucleate cells (Hartwell 1971). Shifting a ts allele of any of these four homologous gene products to restrictive temperature prevented formation of what appeared to be rings of highly ordered membrane-associated filaments at the bud neck (Byers and Goetsch 1976). Antibody decoration (Haarer and Pringle 1987;Ford and Pringle 1991;Kim et al. 1991) and, later, use of fusions to green fluorescent protein (GFP) (Cid et al. 1998) demonstrated that these four proteins colocalized with and were likely constituents of these filaments. Because loss of the function of these proteins prevents cytokinesis and cell septation, and they seemed to be integral components of the filamentous structures erected at the bud neck, they were dubbed septins (Sanders and Field 1994;Pringle 2008). Indeed, subsequent purification of these proteins from yeast (Frazier et al. 1998), and their production as recombinant proteins in bacteria Versele and Thorner 2004;Farkasovsky et al. 2005), demonstrated that Cdc3, Cdc10, Cdc11...

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Section: Evidence For Heterotypic Octamer-octamer Interaction In Vivomentioning

confidence: 99%

Section: Assessment Of the Roles Of The A0 Helix And Its Basic Residumentioning

confidence: 99%

mentioning

confidence: 99%

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Comprehensive Genetic Analysis of Paralogous Terminal Septin Subunits Shs1 and Cdc11 inSaccharomyces cerevisiae

et al. 2015

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“…The relative simplicity of the septin gene family in Drosophila (having 5 septin genes compared to 13 septin genes in human (Fung, Dai, & Trimble, 2014)) and the fact that the Drosophila embryo is amenable to high-resolution live fluorescence imaging makes it a powerful genetically tractable model system for studying a wide spectrum of septin functions in essential cell biological processes, including cell cycle regulation, cytoskeleton and membrane remodeling, and tissue morphogenesis.…”

Section: Introductionmentioning

confidence: 99%

Visualizing septins in early Drosophila embryos

Mavrakis¹

2016

Methods in Cell Biology

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Functional studies in Drosophila have been key for establishing a role for the septin family of proteins in animal cell division and thus extending for the first time observations from the budding yeast to animal cells. Visualizing the distribution of specific septins in different Drosophila tissues and, in particular, in the Drosophila embryo, together with biochemical and mutant phenotype data, has contributed important advances to our understanding of animal septin biology, suggesting roles in processes other than in cytokinesis. Septin localization using immunofluorescence assays has been possible due to the generation of antibodies against different 2 Drosophila septins. The recent availability of lines expressing fluorescent protein fusions of specific septins further promises to facilitate studies on septin dynamics.Here, we provide protocols for preparing early Drosophila embryos to visualize septins using immunofluorescence assays and live fluorescence microscopy. The genetic tractability of the Drosophila embryo together with its amenability to high resolution fluorescence microscopy promise to provide novel insights into animal septin structure and function.

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“…These epigenetic events combined with diseasecausing mutations provide a selective advantage for cancer initiation and progression. Multiple studies have shown that septin 9 gene spanning a region of 219 kb in the genome and encoding different isoforms is epigenetically modified in the promoter region, and can be used as a diagnostic test for CRC [6][7][8].…”

Section: Introductionmentioning

confidence: 99%