The cytochrome C multigene family of rat contains approximately 30 processed pseudogenes that represent genomic DNA copies of three alternate mRNAs. Here, the DNA sequence of an unusual processed pseudogene reveals that it has a complete 3′ noncoding region including a short poly A tail but unlike the others is abruptly truncated at its 5′ end, 19 amino acid codons from the translation terminator. At this position the pseudogene is fused through 17 consecutive adenylic acid residues to a 1.3 kb repeti tive sequence. This repetitive element is flanked by direct repeats and represents a truncated member from a major long interspersed repeat family. The rat element is a composite of sequences observed in long interspersed repeats from both rodents and primates. Comparison to the equivalent mouse sequences shows that the 5′ half of the repeat distal to the pseudogene has an open reading frame and is highly conserved whereas the half adjacent to the pseudogene is evolutionarily unstable. The proportion of cytochrome C pseudogene recombinant clones containing this repetitive DNA is 3 fold greater than observed in random isolates and may reflect a qeneral tendency of processed pseudogenes to associate with other repetitive sequences in the genome.
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