The C. elegans DYRK Kinase MBK-2 Marks Oocyte Proteins for Degradation in Response to Meiotic Maturation.

Howard Hughes Medical Institute and Department of Molecular Biology and Genetics, Johns Hopkins School of Medicine, 725 N. Wolfe St., PCTB 706, Baltimore, Maryland 21205, USA.
Current Biology (Impact Factor: 9.49). 02/2006; 16(1):56-62. DOI: 10.1016/j.cub.2005.11.063
Source: PubMed

ABSTRACT The oocyte-to-embryo transition transforms a differentiated germ cell into a totipotent zygote capable of somatic development. In C. elegans, several oocyte proteins, including the meiotic katanin subunit MEI-1 and the oocyte maturation protein OMA-1, must be degraded during this transition . Degradation of MEI-1 and OMA-1 requires the dual-specificity YAK-1-related (DYRK) kinase MBK-2 . Here, we demonstrate that MBK-2 directly phosphorylates MEI-1 and OMA-1 in vitro and that this activity is essential for degradation in vivo. Phosphorylation of MEI-1 by MBK-2 reaches maximal levels after the meiotic divisions, immediately preceding MEI-1 degradation. MEI-1 phosphorylation and degradation still occur in spe-9 eggs, which undergo meiotic maturation and exit in the absence of fertilization . In contrast, MEI-1 phosphorylation and degradation are blocked in cell-cycle mutants that arrest during the meiotic divisions, and are accelerated in wee-1.3(RNAi) oocytes, which prematurely enter meiotic M phase (A. Golden, personal communication). A GFP:MBK-2 fusion relocalizes from the cortex to the cytoplasm during the meiotic divisions, and this relocalization also depends on cell-cycle progression. Our findings suggest that regulators of meiotic M phase activate a remodeling program, independently of fertilization, to prepare eggs for embryogenesis.

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