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A complex containing the Sm protein CAR-1 and the RNA helicase CGH-1 is required for embryonic cytokinesis in Caenorhabditis elegans.

Audhya A, Hyndman F, McLeod IX, Maddox AS, Yates JR, Desai A, Oegema K - J. Cell Biol. (2005)

Bottom Line: Inhibition of CAR-1 by RNA-mediated depletion or mutation results in a specific defect in embryonic cytokinesis.This cytokinesis failure likely results from an anaphase spindle defect in which interzonal microtubule bundles that recruit Aurora B kinase and the kinesin, ZEN-4, fail to form between the separating chromosomes.Cumulatively, our results suggest that CAR-1 functions with CGH-1 to regulate a specific set of maternally loaded RNAs that is required for anaphase spindle structure and cytokinesis.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA. aaudhya@ucsd.edu

ABSTRACT
Cytokinesis completes cell division and partitions the contents of one cell to the two daughter cells. Here we characterize CAR-1, a predicted RNA binding protein that is implicated in cytokinesis. CAR-1 localizes to germline-specific RNA-containing particles and copurifies with the essential RNA helicase, CGH-1, in an RNA-dependent fashion. The atypical Sm domain of CAR-1, which directly binds RNA, is dispensable for CAR-1 localization, but is critical for its function. Inhibition of CAR-1 by RNA-mediated depletion or mutation results in a specific defect in embryonic cytokinesis. This cytokinesis failure likely results from an anaphase spindle defect in which interzonal microtubule bundles that recruit Aurora B kinase and the kinesin, ZEN-4, fail to form between the separating chromosomes. Depletion of CGH-1 results in sterility, but partially depleted worms produce embryos that exhibit the CAR-1-depletion phenotype. Cumulatively, our results suggest that CAR-1 functions with CGH-1 to regulate a specific set of maternally loaded RNAs that is required for anaphase spindle structure and cytokinesis.

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Cytokinesis fails in car-1 mutant embryos. (A) Schematic illustration of the domain structure of CAR-1. Polyclonal antibodies were generated against the underlined region. (B) Selected panels from time-lapse DIC sequences of wild-type embryos (left column), car-1(RNAi) embryos (middle column), and car-1(tm1753) mutant embryos (right column). Time in seconds after apparent chromosome alignment is indicated in the lower right corner of each panel. (See also Videos 1–3). Bar, 10 μm.
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fig1: Cytokinesis fails in car-1 mutant embryos. (A) Schematic illustration of the domain structure of CAR-1. Polyclonal antibodies were generated against the underlined region. (B) Selected panels from time-lapse DIC sequences of wild-type embryos (left column), car-1(RNAi) embryos (middle column), and car-1(tm1753) mutant embryos (right column). Time in seconds after apparent chromosome alignment is indicated in the lower right corner of each panel. (See also Videos 1–3). Bar, 10 μm.

Mentions: RNAi-based functional genomic screens of C. elegans, in which embryos that were laid by RNA-treated worms were imaged by DIC microscopy, identified several genes that are required for cytokinesis (Gönczy et al., 2000; Piano et al., 2000; Zipperlen et al., 2001; Sönnichsen et al., 2005). One of these, Y18D10a.17, was a previously uncharacterized, but widely conserved, 340-aa protein containing a predicted RGG box and an atypical Sm domain, two motifs that are found commonly in RNA-binding proteins (Fig. 1 A). Consistent with the sequence predictions, purified GST fusions with the Sm domain and the RGG box bound to immobilized RNA (poly(U)-sepharose) beads (Fig. S1; available at http://www.jcb.org/cgi/content/full/jcb.200506124/DC1). Based on the primary sequence features and depletion phenotype, we and other investigators have named this gene car-1, for cytokinesis/apoptosis/RNA.


A complex containing the Sm protein CAR-1 and the RNA helicase CGH-1 is required for embryonic cytokinesis in Caenorhabditis elegans.

Audhya A, Hyndman F, McLeod IX, Maddox AS, Yates JR, Desai A, Oegema K - J. Cell Biol. (2005)

Cytokinesis fails in car-1 mutant embryos. (A) Schematic illustration of the domain structure of CAR-1. Polyclonal antibodies were generated against the underlined region. (B) Selected panels from time-lapse DIC sequences of wild-type embryos (left column), car-1(RNAi) embryos (middle column), and car-1(tm1753) mutant embryos (right column). Time in seconds after apparent chromosome alignment is indicated in the lower right corner of each panel. (See also Videos 1–3). Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171198&req=5

fig1: Cytokinesis fails in car-1 mutant embryos. (A) Schematic illustration of the domain structure of CAR-1. Polyclonal antibodies were generated against the underlined region. (B) Selected panels from time-lapse DIC sequences of wild-type embryos (left column), car-1(RNAi) embryos (middle column), and car-1(tm1753) mutant embryos (right column). Time in seconds after apparent chromosome alignment is indicated in the lower right corner of each panel. (See also Videos 1–3). Bar, 10 μm.
Mentions: RNAi-based functional genomic screens of C. elegans, in which embryos that were laid by RNA-treated worms were imaged by DIC microscopy, identified several genes that are required for cytokinesis (Gönczy et al., 2000; Piano et al., 2000; Zipperlen et al., 2001; Sönnichsen et al., 2005). One of these, Y18D10a.17, was a previously uncharacterized, but widely conserved, 340-aa protein containing a predicted RGG box and an atypical Sm domain, two motifs that are found commonly in RNA-binding proteins (Fig. 1 A). Consistent with the sequence predictions, purified GST fusions with the Sm domain and the RGG box bound to immobilized RNA (poly(U)-sepharose) beads (Fig. S1; available at http://www.jcb.org/cgi/content/full/jcb.200506124/DC1). Based on the primary sequence features and depletion phenotype, we and other investigators have named this gene car-1, for cytokinesis/apoptosis/RNA.

Bottom Line: Inhibition of CAR-1 by RNA-mediated depletion or mutation results in a specific defect in embryonic cytokinesis.This cytokinesis failure likely results from an anaphase spindle defect in which interzonal microtubule bundles that recruit Aurora B kinase and the kinesin, ZEN-4, fail to form between the separating chromosomes.Cumulatively, our results suggest that CAR-1 functions with CGH-1 to regulate a specific set of maternally loaded RNAs that is required for anaphase spindle structure and cytokinesis.

View Article: PubMed Central - PubMed

Affiliation: Ludwig Institute for Cancer Research, Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA. aaudhya@ucsd.edu

ABSTRACT
Cytokinesis completes cell division and partitions the contents of one cell to the two daughter cells. Here we characterize CAR-1, a predicted RNA binding protein that is implicated in cytokinesis. CAR-1 localizes to germline-specific RNA-containing particles and copurifies with the essential RNA helicase, CGH-1, in an RNA-dependent fashion. The atypical Sm domain of CAR-1, which directly binds RNA, is dispensable for CAR-1 localization, but is critical for its function. Inhibition of CAR-1 by RNA-mediated depletion or mutation results in a specific defect in embryonic cytokinesis. This cytokinesis failure likely results from an anaphase spindle defect in which interzonal microtubule bundles that recruit Aurora B kinase and the kinesin, ZEN-4, fail to form between the separating chromosomes. Depletion of CGH-1 results in sterility, but partially depleted worms produce embryos that exhibit the CAR-1-depletion phenotype. Cumulatively, our results suggest that CAR-1 functions with CGH-1 to regulate a specific set of maternally loaded RNAs that is required for anaphase spindle structure and cytokinesis.

Show MeSH
Related in: MedlinePlus