Biphasic activation of Aurora-A kinase during the meiosis I- meiosis II transition in Xenopus oocytes.
Xenopus Aurora-A (also known as Eg2) is a member of the Aurora family of mitotic serine/threonine kinases. In Xenopus oocytes, Aurora-A phosphorylates and activates a cytoplasmic mRNA polyadenylation factor (CPEB) and therefore plays a pivotal role in MOS translation. However, hyperphosphorylation and activation of Aurora-A appear to be dependent on maturation-promoting factor (MPF) activation. To resolve this apparent paradox, we generated a constitutively activated Aurora-A by engineering a myristylation signal at its N terminus. Injection of Myr-Aurora-A mRNA induced germinal vesicle breakdown (GVBD) with the concomitant activation of MOS, mitogen-activated protein kinase, and MPF. Myr-Aurora-A-injected oocytes, however, appeared to arrest in meiosis I with high MPF activity and highly condensed, metaphase-like chromosomes but no organized microtubule spindles. No degradation of CPEB or cyclin B2 was observed following GVBD in Myr-Aurora-A-injected oocytes. In the presence of progesterone, the endogenous Aurora-A became hyperphosphorylated and activated at the time of MPF activation. Following GVBD, Aurora-A was gradually dephosphorylated and inactivated before it was hyperphosphorylated and activated again. This biphasic pattern of Aurora-A activation mirrored that of MPF activation and hence may explain meiosis I arrest by the constitutively activated Myr-Aurora-A.
Ma
Chunqi
C
Ottawa Health Research Institute, Ottawa Hospital Civic Campus, University of Ottawa, Ottawa, Ontario, Canada.
Cummings
Cathy
C
Liu
X Johné
XJ
D000818:Animals; D064127:Aurora Kinases; D018797:Cell Cycle Proteins; D019926:Cyclin B / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D015151:Immunoblotting; D020935:MAP Kinase Signaling System; D008540:Meiosis; D018613:Microscopy, Confocal; D008938:Mitosis; D019814:Myristic Acid / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014981:Xenopus; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D019926:Cyclin B; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D029702:Schizosaccharomyces pombe Proteins; C051655:Suc1 protein, S pombe; D029867:Xenopus Proteins; D019814:Myristic Acid; D011494:Protein Kinases; C112134:AURKA protein, Xenopus; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases