The C. elegans DYRK Kinase MBK-2 Marks Oocyte Proteins for Degradation in Response to Meiotic Maturation.
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.
Stitzel
Michael L
ML
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.
Pellettieri
Jason
J
Seydoux
Geraldine
G
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000201:enzymology; D008540:Meiosis / Q000502:physiology*; D009865:Oocytes / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; C440205:OMA-1 protein, C elegans; C478059:MBK-2 protein, C elegans; D011505:Protein-Tyrosine Kinases; D000251:Adenosine Triphosphatases; C086678:MEI-1 protein, C elegans