Ribosomal-protein synthesis is not autogenously regulated at the translational level in Xenopus laevis

Whether ribosomal-protein synthesis in Xenopus laevis is autogenously controlled at the translational level as is known to occur in prokaryotes has been studied. For this purpose ribosomal (r) proteins were prepared from X. laevis ribosomal subunits and group fractionated by ion-exchange chromatography. They were then added to an in vitro translation system directed by an oocyte mRNA fraction which contains template activity for r proteins. The synthesized radioactive products were analyzed by 2D gel electrophoresis and compared with controls. Similarly in vivo experiments were performed by microinjection of the fractionated proteins into the cytoplasm of Xenopus oocytes followed by incubation with [35S]methionine for different times. In all the experiments no evident effect of r proteins on the translation of their own mRNA was observed.