CO-ORDINATED SYNTHESIS OF SOME RIBOSOMAL PROTEINS AND RIBOSOMAL RNA IN EMBRYOS OF XENOPUS-LAEVIS

The synthesis of ribosomal proteins has been studied in embryos of Xenopus laevis in order to determine whether they are synthesized co-ordinately with ribosomal RNA. A method was devised for isolating ten proteins of the large ribosomal subunit from protein extracts of whole cell homogenates and this method was used to assay for ribosomal protein synthesis in embryos. Cleaving embryos which do not synthesize ribosomal RNA or assemble new ribosomes were found to synthesize or accumulate less than 0.05% of their newly synthesized protein as ribosomal proteins. Mutant anucleolate (0-nu) embryos which are deleted of their genes for 28 and 18 s ribosomal RNA synthesize or accumulate less than 4% as much of these ribosomal proteins as do normal embryos at the same developmental stages. It is concluded that at least these ten ribosomal proteins are synthesized and accumulated co-ordinately with ribosomal RNA. © 1969.