A human 28S ribosomal RNA retropseudogene.

ABSTRACT

A human genomic clone designated LhrRAX3 isolated from an X chromosome-specific library was found to have a 28S ribosomal RNA retropseudogene symbolized as RNRP2 within a 12.5-kb human DNA insert. The sequence of the rRNA retropseudogene has an identity of 96% with about 300 nucleotides at the 3'-terminus of the human 28S rRNA gene. RNRP2 is flanked by a pair of perfect direct repeats of 16 nucleotides, the hallmark characteristic of a processed pseudogene having been integrated into the genome. The structural element has a long A-rich tract at its 3'-end, apparently the result of an aberrant polyadenylation event of a RNA polymerase I transcript, prior to its subsequent reverse transcription and retroposition into the genome. An Alu repeat sequence truncated by 80 nucleotides at the 5'-region occurs about 800 base pairs downstream and is of opposite orientation to RNRP2. The Alu element is bounded by 16-nucleotide direct repeats and is a member of the Alu Y subfamily.