Regulation of protein biosynthesis during plaice (Pleuronectus platessa) embryogenesis

Abstract

The regulation of protein biosynthesis at fertilisation was studied in North Sea Plaice (Pleuronectus platessa). RNA and protein synthesis were studied in fertilised and unfertilised plaice eggs. There was no detectable RNA synthesis in the egg in early embryonic stages, but protein synthesis at all stages of development. However, using RITA synthesis inhibitors (actinomycin D and ethidium bromide), it was demonstrated that certain groups of proteins were synthesised independently of any newly synthesised messenger RNA. Different rates of protein synthesis in various subcellular fractions from both fertilised and unfertilised eggs were demonstrated. Proteins precipitated by vinblastine were shown to exhibit the most changes between the egg and fertilised egg. These proteins were further characterized on several polyacrylamide-gel electrophoresis systems. RNA was isolated from the polysomes and the supernatant fractions of eggs and fertilised eggs. This RITA was tested for messenger RITA activity in a rabbit reticulocyte cell-free system and also in a wheat germ in vitro system. Messenger RNA activity was demonstrated in both the polysomal and supernatant fractions from the egg and also from the fertilised egg, and was purified by affinity chromatography and sucrose gradient centrifugation. Regulatory mechanisms have been demonstrated at the translational level of protein synthesis in early plaice embryogenesis.