CLONING AND SEQUENCE OF A PROCESSED P53 PSEUDOGENE FROM RAT - A POTENTIAL SOURCE OF FALSE MUTATIONS IN PCR FRAGMENTS OF TUMOR DNA

We describe here the nucleotide (nt) sequence of a p53 processed pseud ogene (psi-gene) from the normal F344 rat genome. Exon-derived primers were utilized to amplify and clone a 1447-bp polymerase chain reactio n (PCR) product corresponding to the coding regions of exons 2-11 of t he functional gene, This psi-gene is a cDNA-like sequence possessing 8 7% homology with the functional rat p53. We have also partially charac terized two additional and distinctly different putative rat p53 psi-g enes, focussing on the sequences surrounding the reported rat p53 muta tional hot spots of codons 202(R) and 211(R) within exon 6/7, Each of these three psi-gene sequences contained various single- and/or double -nt substitutions, small deletions and insertions that distinguish the m from p53, One substitution, 211(R) CGG-->CAG, found both in the clon ed psi-gene and in one of the partially characterized, putative psi-ge nes, corresponded precisely with the sequence that has been reported a s a mutation at one of the hot spots. Co-amplification of one or more of the p53 psi-genes with portions of the functional p53 is likely, if exon-based primers are utilized for PCR amplification of rat p53. Con sequently, psi-gene sequences are potential sources of sequence variat ions that can be misidentified as somatic cell mutations by direct seq uencing of inappropriately generated PCR products.