Expression of ribosomal protein genes and regulation of ribosome biosynthesis in Xenopus development

Studies on ribosome biosynthesis in developing Xenopus oocytes and embryos, and after microinjection of cloned ribosomal-protein genes, have revealed that the synthesis of ribosomal proteins (r-proteins) is controlled by two types of regulation: (1) a post-transcriptional regulation, operated by feedback of the r-proteins themselves, controls processing and stability of r-protein transcripts and thus the amount of the corresponding mRNA present in the cell; and (2) a translational regulation controls the efficiency of utilization of r-protein mRNA (rp-mRNA) in response to the cellular needs for new ribosomes.