The mobilization of maternal histone messenger RNA after fertilization of the sea urchin egg.

The extent of protein, RNA and DNA synthesis in early cleavage stages of the sea urchin embryo (Parechinus angulosus) was determined. A histone mRNA specific cDNA was used in hybridization experiments to investigate the cytoplasmic localization of maternal histone mRNA in the unfertilized sea urchin egg and first cleavage stage embryo. In the unfertilized egg histone mRNA was localized exclusively in ribonucleoprotein particles with none in ribosomes or polyribosomes. This distribution changed after fertilization, in particular, coupled with the first cleavage telophase there was a significant transfer of histone mRNA from the ribonucleoprotein fraction to the polyribosomes. The results indicate mRNA specific translational control mechanisms.