Reverse-transcribed pseudogenes of U1 small nuclear RNA presumably amplified in the rat genome together with the flanking region.
We have examined 25 independent rat genomic clones each of which contains a U1 RNA gene or a pseudogene. We have found five clones whose restriction maps are identical with or overlapping one another. These clones contain sequences which are co-linear with that of U1 RNA except for one or two nucleotides (nt). They also contain 21-23-nt poly(A) stretches immediately after U1 RNA homology. In addition, the U1 RNA-poly(A) regions are surrounded by the same direct repeat sequences. Therefore, they seem to be pseudogenes which have been generated by the reverse transcription of poly(A)-tailed U1 RNA followed by the insertion of the transcript into the genome. Furthermore, conservation of the sequences extends over at least 18 kb of the flanking sequences. This suggests a family of conserved reverse-transcribed pseudogenes, which implies amplification of an original pseudogene. It is also suggested that the target sequence without insertion of a U1 RNA sequence has been amplified. The mechanisms for the amplification and sequence conservation are discussed.
D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification; D004262:DNA Restriction Enzymes; D005784:Gene Amplification; D005796:Genes; D008099:Liver / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000235:genetics*; D051381:Rats; D011919:Rats, Inbred Strains; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic
D012342:RNA, Small Nuclear; D004247:DNA; D004262:DNA Restriction Enzymes