Cytoplasmic regulation of translation during llyanassa embryogenesis

Summary Two-dimensional electrophoresis of labeled proteins and hybridization of mRNAs with specific gene probes was used to demonstrate changes in protein synthesis, and the cytoplasmic control of actin maternal mRNAs during the early development of llyanassa. The isolated polar lobe was used as a nucleus-free egg fragment to study the regulation of translation. It was shown that actin mRNAs are present in the unfertilized egg and are therefore maternal in origin, are inactive during early cleavage, and are translated in normal, lobeless, actinomycin D-treated blastulae and in isolated polar lobes that have been aged for 24 h. Thus, the activation of actin mRNAs is controlled by cytoplasmic factors that function independently of cleavage and nuclear activity. I suggest that the running of a cytoplasmic clock determines when maternal mRNAs are activated, and that this clock is made and set running during oogenesLs. Changes in protein synthesis that occurred during early cleavage were shown to also involve the diminution of some early cleavage proteins, and it was suggested that this diminution is controlled by cytoplasmic factors localized in the blastomeres of the lobeless egg but absent from the polar lobe.