Affiliation:
1. Ottawa Health Research Institute, Ottawa Hospital Civic Campus
2. Department of Biochemistry, Microbiology and Immunology
3. Department of Obstetrics and Gynaecology, University of Ottawa, Ottawa, Ontario, Canada
Abstract
ABSTRACT
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.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
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