Research is being conducted on the mechanism(s) involved in the induction of oocyte maturation (amphibian) with steroid hormones. The events of maturation have been divided temporally into """"""""early"""""""" and """"""""late"""""""" responses to the steroid (progesterone). The early change includes an almost immediate increase in free calcium activity the effects of which appear to be mediated by the calcium binding protein calmodulin. The role of calmodulin is being monitored by isolation of proteins which bind to calmodulin affinity columns coupled with in vitro and in vivo assays of enzymatic activities of these proteins. The late events of maturation include an increase in the rate of protein synthesis. We are studying the nature and control of this steroid-induced rate change by monitoring possible changes in initiation and elongation rates in control versus maturing oocytes. We also have microinjected various heterologous mRNAs into oocytes followed by assays for intracellular distribution of the messages (soluble versus membrane bound polysomes) and by assays for the degree of competition between the injected mRNAs and between the injected mRNAs and endogenous messages. In this way, we hope to determine whether factors which may be rate limiting for protein synthesis are localized and whether or not the distribution of such materials changes during oocyte maturation.
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