Chromosome condensation in pig oocytes: lack of a requirement for either cdc2 kinase or MAP kinase activity.
In this study, butyrolactone I (BL I), a potent and specific inhibitor of cyclin-dependent kinases (cdk), is shown to inhibit germinal vesicle breakdown (GVBD) in pig oocytes. Oocytes treated with 100 microM BL I were arrested in the germinal vesicle (GV)-stage and displayed low activity of cdc2 kinase and MAP kinase. Nevertheless, chromosome condensation occurred and highly condensed bivalents were seen within an intact GV after a 24-hr culture in the presence of BL I. The inhibitory effect of BL I on MAP kinase activation during culture was likely mediated through a cdk-dependent pathway, since MAP kinase activity present in extracts derived from metaphase II eggs was not inhibited by BL I. The block of GVBD could be released by treating oocytes with okadaic acid (OA), an inhibitor of type 1 and 2A phosphatases; 82% of the oocytes treated with the combination of OA/BL I underwent GVBD, and MAP kinase became activated, while cdc2 kinase remained inhibited. These results suggest that both chromosome condensation and GVBD could occur without activation of cdc2 kinase, whereas an increase in MAP kinase activity may be a requisite for GVBD in pig oocytes in conditions when cdc2 kinase activation is blocked by BL I.
Kubelka
Michal
M
Department of Physiology of Reproduction, Institute of Animal Physiology and Genetics, Libechov, Czech Republic. Kubelka@iapg.cas.cz
Anger
Martin
M
Kalous
Jaroslav
J
Schultz
Richard M
RM
Motlík
Jan
J
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D016203:CDC2 Protein Kinase / Q000502:physiology*; D002875:Chromosomes / Q000502:physiology*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D004527:Egg Proteins / Q000037:antagonists & inhibitors / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006657:Histones / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D019319:Okadaic Acid / Q000494:pharmacology; D009865:Oocytes / Q000201:enzymology / Q000648:ultrastructure*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D013552:Swine / Q000235:genetics*
D004527:Egg Proteins; D004791:Enzyme Inhibitors; D006657:Histones; D019319:Okadaic Acid; C082868:butyrolactone I; D016203:CDC2 Protein Kinase; D018844:Cyclin-Dependent Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D015107:4-Butyrolactone