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CSC-1: a subunit of the Aurora B kinase complex that binds to the survivin-like protein BIR-1 and the incenp-like protein ICP-1.

Romano A, Guse A, Krascenicova I, Schnabel H, Schnabel R, Glotzer M - J. Cell Biol. (2003)

Bottom Line: CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo.ICP-1 dramatically stimulates AIR-2 kinase activity.This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology, Dr. Bohrgasse 7, Vienna A-1030, Austria.

ABSTRACT
The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

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csc-1 encodes a 27-kD protein required for chromosome segregation and cytokinesis. (A) csc-1 mutants have defects in chromosome segregation and cytokinesis. Images shown are selected from a time-lapse Nomarski recording of a wild type and an embryo derived from a homozygous csc-1(t1171) mutant hermaphrodite. (B) Schematic depicting the position of the csc-1 locus. SNP mapping placed csc-1 between SNP L and SNP R. (C) csc-1(RNAi) and icp-1(RNAi) cause similar chromosome segregation phenotypes. Embryos dissected from worms expressing GFP–histone H2B and depleted of CSC-1 or ICP-1 by RNAi were imaged by Nomarski and fluorescence optics. Time shown is relative to nuclear envelope breakdown. The GFP signal is shown as a red overlay. (D) The sequence of the CSC-1 protein; the potential coiled-coil region is underlined and the imperfect repeat is double underlined. Glutamine 128, the residue mutated in csc-1(t1171), is indicated by an asterisk.
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fig1: csc-1 encodes a 27-kD protein required for chromosome segregation and cytokinesis. (A) csc-1 mutants have defects in chromosome segregation and cytokinesis. Images shown are selected from a time-lapse Nomarski recording of a wild type and an embryo derived from a homozygous csc-1(t1171) mutant hermaphrodite. (B) Schematic depicting the position of the csc-1 locus. SNP mapping placed csc-1 between SNP L and SNP R. (C) csc-1(RNAi) and icp-1(RNAi) cause similar chromosome segregation phenotypes. Embryos dissected from worms expressing GFP–histone H2B and depleted of CSC-1 or ICP-1 by RNAi were imaged by Nomarski and fluorescence optics. Time shown is relative to nuclear envelope breakdown. The GFP signal is shown as a red overlay. (D) The sequence of the CSC-1 protein; the potential coiled-coil region is underlined and the imperfect repeat is double underlined. Glutamine 128, the residue mutated in csc-1(t1171), is indicated by an asterisk.

Mentions: During a large-scale screen for maternal effect embryonic lethal mutations, we isolated a mutant allele (t1171) that exhibited the set of phenotypes characteristic of the ABI complex members (Fig. 1 A). In particular, meiotic chromosome segregation and polar body extrusion are defective. During mitosis, spindle assembly appears normal, but chromosome segregation fails entirely and a single large nucleus reassembles in the subsequent interphase. After spindle elongation, a cleavage furrow forms and ingresses, but it fails to ingress to completion, thus producing a multinucleate embryo.


CSC-1: a subunit of the Aurora B kinase complex that binds to the survivin-like protein BIR-1 and the incenp-like protein ICP-1.

Romano A, Guse A, Krascenicova I, Schnabel H, Schnabel R, Glotzer M - J. Cell Biol. (2003)

csc-1 encodes a 27-kD protein required for chromosome segregation and cytokinesis. (A) csc-1 mutants have defects in chromosome segregation and cytokinesis. Images shown are selected from a time-lapse Nomarski recording of a wild type and an embryo derived from a homozygous csc-1(t1171) mutant hermaphrodite. (B) Schematic depicting the position of the csc-1 locus. SNP mapping placed csc-1 between SNP L and SNP R. (C) csc-1(RNAi) and icp-1(RNAi) cause similar chromosome segregation phenotypes. Embryos dissected from worms expressing GFP–histone H2B and depleted of CSC-1 or ICP-1 by RNAi were imaged by Nomarski and fluorescence optics. Time shown is relative to nuclear envelope breakdown. The GFP signal is shown as a red overlay. (D) The sequence of the CSC-1 protein; the potential coiled-coil region is underlined and the imperfect repeat is double underlined. Glutamine 128, the residue mutated in csc-1(t1171), is indicated by an asterisk.
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Related In: Results  -  Collection

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fig1: csc-1 encodes a 27-kD protein required for chromosome segregation and cytokinesis. (A) csc-1 mutants have defects in chromosome segregation and cytokinesis. Images shown are selected from a time-lapse Nomarski recording of a wild type and an embryo derived from a homozygous csc-1(t1171) mutant hermaphrodite. (B) Schematic depicting the position of the csc-1 locus. SNP mapping placed csc-1 between SNP L and SNP R. (C) csc-1(RNAi) and icp-1(RNAi) cause similar chromosome segregation phenotypes. Embryos dissected from worms expressing GFP–histone H2B and depleted of CSC-1 or ICP-1 by RNAi were imaged by Nomarski and fluorescence optics. Time shown is relative to nuclear envelope breakdown. The GFP signal is shown as a red overlay. (D) The sequence of the CSC-1 protein; the potential coiled-coil region is underlined and the imperfect repeat is double underlined. Glutamine 128, the residue mutated in csc-1(t1171), is indicated by an asterisk.
Mentions: During a large-scale screen for maternal effect embryonic lethal mutations, we isolated a mutant allele (t1171) that exhibited the set of phenotypes characteristic of the ABI complex members (Fig. 1 A). In particular, meiotic chromosome segregation and polar body extrusion are defective. During mitosis, spindle assembly appears normal, but chromosome segregation fails entirely and a single large nucleus reassembles in the subsequent interphase. After spindle elongation, a cleavage furrow forms and ingresses, but it fails to ingress to completion, thus producing a multinucleate embryo.

Bottom Line: CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo.ICP-1 dramatically stimulates AIR-2 kinase activity.This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology, Dr. Bohrgasse 7, Vienna A-1030, Austria.

ABSTRACT
The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

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