title: CDK-1 and two B-type cyclins promote PAR-6 stabilization during polarization of the early C. elegans embryo.
abstract: In the C. elegans embryo, formation of an antero-posterior axis of polarity relies on signaling by the conserved PAR proteins, which localize asymmetrically in two mutually exclusive groups at the embryonic cortex. Depletion of any PAR protein causes a loss of polarity and embryonic lethality. A genome-wide RNAi screen previously identified two B-type cyclins, cyb-2.1 and cyb-2.2, as suppressors of par-2(it5ts) lethality. We found that the loss of cyb-2.1 or cyb-2.2 suppressed the lethality and polarity defects of par-2(it5ts) mutants and that these cyclins act in cell polarity with their cyclin-dependent kinase partner, CDK-1. Interestingly, cyb-2.1; cyb-2.2 double mutants did not show defects in cell cycle progression or timing of polarity establishment, suggesting that they regulate polarity independently of their typical role in cell cycle progression. Loss of both cyclin genes or of cdk-1 resulted in a decrease in PAR-6 levels in the embryo. Furthermore, the activity of the cullin CUL-2 was required to achieve suppression of par-2 lethality when both cyclins were absent. Our results support a model in which CYB-2.1/2/CDK-1 antagonize CUL-2 activity to promote stabilization of PAR-6 levels during polarization of the early C. elegans embryo. They also suggest that CYB-2.1 and CYB-2.2 contribute to the coupling of cell cycle progression and asymmetric segregation of cell fate determinants.
authors: Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada.
authors: Alexia
authors: A
authors: Rabilotta
authors: Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada.
authors: Marianne
authors: M
authors: Desrosiers
authors: Institute of Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, Quebec, Canada; Department of Pathology and Cell Biology, Université de Montréal, Montréal, Quebec, Canada.
authors: Jean-Claude
authors: JC
authors: Labbé
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000502:physiology; D016203:CDC2 Protein Kinase / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology; D019926:Cyclin B / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D019926:Cyclin B; C512642:par-6 protein, C elegans; D016203:CDC2 Protein Kinase