DYRK2 and GSK-3 phosphorylate and promote the timely degradation of OMA-1, a key regulator of the oocyte-to-embryo transition in C. elegans

Abstract

Oocyte maturation and fertilization initiates a dynamic and tightly regulated process in which a non-dividing oocyte is transformed into a rapidly dividing embryo. We have shown previously that two C. elegans CCCH zinc finger proteins, OMA-1 and OMA-2, have an essential and redundant function in oocyte maturation. Both OMA-1 and OMA-2 are expressed only in oocytes and 1-cell embryos, and need to be degraded rapidly after the first mitotic division for embryogenesis to proceed normally. We report here a distinct redundant function for OMA-1 and OMA-2 in the 1-cell embryo. Depletion of both oma-1 and oma-2 in embryos leads to embryonic lethality. We also show that OMA-1 protein is directly phosphorylated at T239 by the DYRK kinase MBK-2, and that phosphorylation at T239 is required both for OMA-1 function in the 1-cell embryo and its degradation after the first mitosis. OMA-1 phosphorylated at T239 is only detected within a short developmental window of 1-cell embryos, beginning soon after the proposed activation of MBK-2. Phosphorylation at T239 facilitates subsequent phosphorylation of OMA-1 by another kinase, GSK-3, at T339 in vitro. Phosphorylation at both T239 and T339 are essential for correctly-timed OMA-1 degradation in vivo. We propose that a series of precisely-timed phosphorylation events regulates both the activity and the timing of degradation for OMA proteins, thereby allowing restricted and distinct functions of OMA-1 and OMA-2 in the maturing oocyte and 1-cell embryo, ensuring a normal oocyte-to-embryo transition in C. elegans.

Regulation of RCAN1 Protein Activity by Dyrk1A Protein-mediated Phosphorylation

“…RCAN1 phosphorylation by GSK3␤ did not occur with proteins carrying mutations at S108A and S112A, which are the sites of GSK3␤ and Dyrk1A phosphorylation, respectively. In the priming experiment with the T192A mutant, the Dyrk1A-prephosphorylated RCAN1 was as strongly phosphorylated by GSK3␤ as was the wild-type RCAN1, excluding the possibility of noncanonical GSK3 priming (the priming kinase phosphorylates a residue required for GSK3␤ phosphorylation not at the ϩ4-position), which has been shown for mammalian Dyrk1A kinase on NFAT (5) and for the Dyrk1A orthologue MBK-2 in Caenorhabditis elegans (34). These results suggest that Dyrk1A-mediated phosphorylation of Ser 112 primes RCAN1 A, Coomassie staining of SDS-polyacrylamide gels containing purified recombinant Dyrk1A WT and Y321F and RCAN1 proteins (left).…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part II. Kinase Regulators and Substrates

“…elegans EGG-3 is a member of protein-tyrosine phosphatase-like (PTPL) family, whose mutant egg undergoes fertilization normally but has a defect in polarized dispersal of Factin, formation of chitin eggshell, and production of polar bodies (Maruyama et al 2007). Although enzymatic substrate for has not yet been demonstrated (PTPL proteins are supposed to be pseudo-phosphatase), its functional interaction with CHS-1, which is required for deposition of egg shell, plays a role for proper distribution of MBK-2 kinase that regulates degradation of maternal proteins and egg-to-embryo transition (Nishi and Lin 2005;Qu et al 2006;Qu et al 2007;Stitzel et al 2007;Stitzel et al 2006). Other members of PTPL family such as EGG-4 and EGG-5 have also been characterized as components of meiotic cell cycle progression and egg-to-embryo transition.…”

“…OMA-1 protein is largely reduced because of rapid degradation after the first mitotic division and this is necessary for the early embryonic development by regulating the temporal degradation of maternal proteins in early C. elegans embryos (Lin 2003;Shimada et al 2006;Shirayama et al 2006). OMA-1 is directly phosphorylated (Thr-239) by DYRK kinase MBK-2 that facilitates subsequent phosphorylation (Thr-339) by another kinase GSK-3 and these precisely timed phosphorylation events are important for its function in 1-cell embryo and degradation after first mitosis (Nishi and Lin 2005).…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part I. Protein Kinases

“…In nematode oocytes, DYRK2/MBK2, a member of DYRK, in cooperation with CDK1 (this kinase catalyses activating phosphorylation of MBK-2 on Ser-68) (Cheng et al 2009), GSK3, and Kin-19, phosphorylates and promotes degradation of OMA-1 that regulates oocyte-to-embryo transition (Nishi and Lin 2005;Qu et al 2006;Qu et al 2007;Stitzel et al 2007;Stitzel et al 2006). In Xenopus oocytes, Ras-dependent oocyte maturation involves the function of DYRK1A (Qu et al 2006;Qu et al 2007).…”

“…GSK3/shaggy along with other downstream components of the Wnt pathway mediate patterning along the primary animal-vegetal axis of the sea urchin embryo (Emily-Fenouil et al 1998) and along the dorsal-ventral axis in Xenopus, suggesting a conserved basis for axial patterning between invertebrate and vertebrate. Double phosphorylation (Thr-239 by DYRK kinase MBK-2 and Thr-339 by GSK-3) on OMA-1 is essential for correctly timed degradation of OMA-1 and ensures a normal oocyte-to-embryo transition in C. elegans (Nishi and Lin 2005). Even the conserved function of GSK3 is observed in hydra embryogenesis (Rentzsch et al 2005), and in zebrafish cardiogenesis (Emily-Fenouil et al 1998;Lee et al 2007;Liu et al 2007;Nishi and Lin 2005;Uzbekova et al 2009).…”