The cDNA for the ubiquitin-52-amino-acid fusion protein from rat encodes a previously unidentified 60 S ribosomal subunit protein

Rat cDNAs for a 52-amino-acid ribosomal protein (CEP52) that is typically formed as a ubiquitin fusion protein, were cloned following reverse transcription and PCR amplification. CEP52 sequence conservation is demonstrated by the similarity of the human and rat cDNA sequences and the identity of the predicted proteins. Amplification of rat cDNA with a primer specific for the 3' non-coding region of the CEP52 gene, in combination with a consensus primer for the 5' end of the ubiquitin coding sequence, provided evidence that the rat CEP52 gene is fused to a ubiquitin reading frame. Direct sequence analysis of this PCR product confirmed the in-frame fusion of a ubiquitin coding sequence to the rat CEP52 gene. Antibodies against a synthetic CEP52 peptide were used to show that expressed CEP52 is associated with the 60 S ribosomal subunit, and that it is not linked to ubiquitin. The quantity of CEP52 found in different tissues is quite variable, but appears to correspond to the amount of ribosomes present. Although the human, Arabidopsis thaliana and Nicotiana tabacum CEP52 genes contain introns within the CEP52 coding region, the rat CEP52 coding sequence appears to lack insertions.