Splicing Control and Nucleus/Cytoplasm Compartmentalization of Ribosomal Protein L1 RNA in X. Laevis Oocytes

Abstract

In X. laevis, the gene encoding for the r-protein L1 is post-transcriptionally regulated. In the presence of excess amounts of free L1 r-protein a specific pre-mRNA which contains the third intron of the gene is accumulated. In the absence of splicing the pre-mRNA is degraded leading to the reduction of the mRNA levels available for translation. A model has been proposed in which the L1 r-protein can feedback regulate its synthesis by controlling the efficiency of splicing of its own precursor RNA (Bozzoni et al., 1984). In order to simplify the analysis of the splicing process we have constructed plasmids in which specific exon-intron-exon portions of the L1 gene have been cloned in front of the CAT gene. When injected in X. laevis nuclei they direct the synthesis of the CAT enzyme only if the intron is spliced out. Using this system we have studied the splicing of the third intron and the role of intron removal in the process of mRNA transport to the cytoplasm.