Beck P, Dingermann T, Winckler T. Transfer RNA gene-targeted retrotransposition of Dictyostelium TRE5-A into a chromosomal UMP synthase gene trap.
J Mol Biol 2002;
318:273-85. [PMID:
12051837 DOI:
10.1016/s0022-2836(02)00097-9]
[Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The genome of the eukaryotic microorganism Dictyostelium discoideum hosts a family of seven non-long terminal repeat retrotransposons (TREs) that show remarkable insertion preferences near tRNA genes. We developed an in vivo assay to detect tRNA gene-targeted retrotransposition of endogenous TREs in a reporter strain of D. discoideum. A tRNA gene positioned within an artificial intron was placed into the D. discoideum UMP synthase gene. This construct was inserted into the D. discoideum genome and presented as a landmark for de novo TRE insertions. We show that the tRNA gene-tagged UMP synthase gene was frequently disrupted by de novo insertions of endogenous TRE5-A copies, thus rendering the resulting mutants resistant to 5-fluoroorotic acid selection. Approximately 96% of all isolated 5-FOA-resistant clones contained TRE5-A insertions, whereas the remaining 4% resulted from transposition-independent mutations. The inserted TRE5-As showed complex structural variations and were found about 50 bp upstream of the reporter tRNA gene, similar to previously analysed genomic copies of TRE5-A. No integration by other members of the TRE family was observed. We found that only 51% of the de novo insertions were derived from autonomous TRE5-A.1 copies. The remaining 49% of new insertions were due to TRE5-A.2 elements, which lack the proteins required for reverse transcription and integration, but retain functional promoter sequences.
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