Retrotransposon transposition intermediates are encapsidated into virus-like particles.

Virus-like particles (VLPs) possessing reverse transcriptase activity are persistently present in Drosophila melanogaster cultured cells and are formed in yeast induced for transposition. Different retrotransposon transposition intermediates consistent with those expected from the model of reverse transcription pathway of retrotransposon transposition have been detected during the analysis of nucleic acids isolated from VLPs. These data indicate that the act of reverse transcription takes place in VLPs which may be considered as functional intermediates of transposition.

The steps of reverse transcription of Drosophila mobile dispersed genetic elements and U3-R-U5 structure of their LTRs.

Reverse transcription intermediate forms (minus and plus strong-stop DNA) are detected in Drosophila melanogaster cultured cells for mobile dispersed genetic elements mdg1, mdg3, and mdg4 (gypsy). The mdg elements studied possess a common mechanism of reverse transcription, despite their structural differences, and the comparative analysis of intermediate forms proves that mdg elements pass the same stages of reverse transcription as retroviruses. The length of minus strong-stop DNA that locates the RNA start site coincides with the data obtained from S1 nuclease analysis of transcription initiation.

Reverse transcription of Drosophila mobile dispersed genetic element RNAs: detection of intermediate forms.

DNA-RNA complexes were detected in cultured Drosophila melanogaster cells. These complexes are practically perfect hybrid molecules of mobile dispersed genes DNA (mdg1 and mdg3) and suitable poly(A)+RNA. Three species of single-stranded DNA have been found in hybrid molecules: full-sized mdg DNA containing either one or two LTRs (both minus strands) and single LTR sequences (plus strand).

Circular copies of mobile dispersed genetic elements in cultured Drosophila melanogaster cells.

Extrachromosomal supercoiled circular copies of mobile dispersed genetic elements mdg1, mdg3 and copia have been isolated from 67J25D and Kc lines of cultured Drosophila melanogaster cells. With the exception of the copia element in the line Kc, all circular molecules contain only one long terminal repeat. Both whole-length circular copies and molecules with deletion from the internal segment of the copia element have been detected in the line 67J25D.