The rat genome contains a p53 pseudogene: detection of a processed pseudogene using PCR

The p53 gene is the most frequently mutated gene in human cancer. Our investigation of this gene in radiation-induced tumors led to the discovery of a processed pseudogene in the rat genome. We amplified eight coding exons of the p53 gene using rat liver DNA as template, and, in each case, one major amplification product was apparent on agarose gels. When we selected primers to amplify fragments containing more than one exon, two major products were apparent. In each case, the size of the larger amplification product was consistent with that of the expected p53 fragment. The sizes of the shorter amplification products suggested that these fragments are amplified from a processed p53 pseudogene. When the blotted fragments were probed with sequences internal to the amplification primers, both the gene and putative pseudogene fragments were seen. Sequences of the shorter coamplicons have high homology with the p53 cDNA and cross intron splice junctions. These findings suggest that the rat genome contains a processed p53 pseudogene. The data demonstrate the usefulness of the polymerase chain reaction for revealing processed pseudogenes, and suggest that the pseudogene can be used as an internal control when amplifying the rat p53 gene.