Turnover of R1 (type I) and R2 (type II) retrotransposable elements in the ribosomal DNA of Drosophila melanogaster
Article Abstract:
R1 and R2 are retrotransposable elements which insert site-specifically in the 28S rRNA genes of Drosophila melanogaster. Because of their unique insertion behavior, the level and sequence divergence of R1 and R2 were investigated in 27 strains of D. melanogaster. The results showed that the fraction of rDNA repeats inserted with R1 and R2 varied widely among the strains, although no copies of R1 or R2 were significantly divergent in sequence. A large number of copies have 5' truncated ends. The results indicate that these elements are subject to both retrotransposition and the recombinational forces operational in the rDNA.
Publication Name: Genetics
Subject: Biological sciences
ISSN: 0016-6731
Year: 1992
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Reverse transcription of R2Bm RNA is primed by a nick at the chromosomal target site: a mechanism for non-LTR retrotransposition
Article Abstract:
The mechanism of retrotransposition of retrotransposons without long terminal repeats was elucidated. Previous investigations identified the R2Bm open reading frame of Bombyx mori as coding for an endonuclease capable of cleaving the 28S rRNA gene in Escherichia coli. Further analysis of the purified protein showed that it also possesses reverse transcriptase activity. Reverse transcription ensues upon nicking of the chromosomal target using the 3' hydroxyl group generated in one DNA strand. Cleavage of the second strand occurs after synthesis of the new RNA strand.
Publication Name: Cell
Subject: Biological sciences
ISSN: 0092-8674
Year: 1993
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R1 and R2 retrotransposable elements of Drosophila evolve at rates similar to those of nuclear genes
Article Abstract:
R2 and R1 non-long-terminal repeat retransposable elements have been maintained in the Drosophila melanogaster by vertical germline transmission over a period of 17 to 20 million years. They are located at the 28S ribosomal RNA gene of several insect species. The stability of R2 and R1 maintenance in Drosophila has enabled the substitution of nucleotides in these species. This phenomena has rendered their evolution identical to that of nuclear genes.
Publication Name: Genetics
Subject: Biological sciences
ISSN: 0016-6731
Year: 1995
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