CLONING A PSEUDOGENE AND CDNA-ENCODING A 17-KDA RIBOSOMAL-PROTEIN FROM MOUSE - STRUCTURE AND REGULATION OF EXPRESSION

An rplambda5 cDNA encoding a ribosomal protein (r-protein) and a pseud ogenic form of the corresponding gene (rplambda7) have been cloned fro m mouse. This cDNA codes for a highly basic protein of 160 amino acids (aa) with a deduced M(r) of 17 601, and most likely represents the sp ecies homolog of a recently cloned rat cDNA, which has been proposed t o encode a homolog of the yeast r-protein, YL43. The entire rplambda5 gene encompasses less than 1.5 kb of genomic DNA and apparently is com posed of only two exons, as deduced from sequence comparison with its very similar pseudogenic variant, rplamdab7. Southern analysis, using the rplamda5 cDNA as a probe, indicates the existence of a great numbe r of highly related sequences in the mouse genome. The mRNA for rplamb da5 is approximately 800 nucleotides (nt) long and is found to be ubiq uitously expressed at high levels in embryonic and adult mouse tissues , as shown by Northern and in situ analyses. Retinoic acid (RA) seems to have a moderate down-regulatory effect on this mRNA in differentiat ing P19 embryonal carcinoma cells. Several degenerate/nondegenerate RA -response element (RARE) motifs are found within 560 bp upstream from the degenerate start codon in rplambda7. However, it is unknown whethe r this RA effect is exerted at the transcriptional and/or posttranscri ptional levels.