Rapid evolution of a cyclin A inhibitor gene, roughex, in Drosophila.

The recent sequencing of the complete genome of the fruit fly Drosophila melanogaster has yielded about 30% of the predicted genes with no obvious counterparts in other organisms. These rapidly evolving genes remain largely unexplored. Here, we present evidence for a striking variability in an important Drosophila cell cycle regulator encoded by the gene roughex (rux) in closely related fly species.

Two variants of the Drosophila melanogaster retrotransposon gypsy (mdg4): structural and functional differences, and distribution in fly stocks.

Two variants of the Drosophila melanogaster retrotransposon gypsy were subjected to detailed structural and functional analysis. A series of hybrid constructs containing various combinations of "active" and "inactive" gypsy copies were tested for their ability to produce new DNA copies in cultured cells by means of reverse transcription. It was shown that the previously demonstrated variations in retrotranspositional activity are associated with either one or both of two amino acid substitutions at the beginning of ORF2.

Roughex mediates G(1) arrest through a physical association with cyclin A.

Differentiation in the developing Drosophila eye requires synchronization of cells in the G(1) phase of the cell cycle. The roughex gene product plays a key role in this synchronization by negatively regulating cyclin A protein levels in G(1). We show here that coexpressed Roughex and cyclin A physically interact in vivo.

[Trans-mobilization of deletion copies of the mdg3 retrotransposon in cultured cells of Drosophila].

A model system was studied that was associated with the selective amplification of shortened copies of the mdg3 retrotransposon in cultured cells of Drosophila melanogaster. While full-length mdg3 is present in all species phylogenetically closely related to D. melanogaster, the distribution of its deletion copy mdg3del was shown to be restricted only to D.

[Features of the structure of the 7K-copy of Drosophila MDG4 (gypsy) retrotransposon provides evidence that the 7K-subfamily of MDG4 is potentially capable of transposition].

The complete nucleotide sequence of the 7K variant of the gypsy retrotransposon of Drosophila melanogaster was determined. This variant belongs to the 7K subfamily of gypsy, which was previously considered inactive. All differences found in the sequenced 7K copy compared to the transpositionally active 6K variants were point mutations.

Identification of spliced RNA species of Drosophila melanogaster gypsy retrotransposon. New evidence for retroviral nature of the gypsy element.

We have identified a novel RNA species of Drosophila melanogaster gypsy retrotransposon that is ca. 2 kb in length and corresponds to the third open reading frame (ORF3) of the gypsy element. This RNA is generated by splicing of the primary gypsy transcript, as is the case for retroviral env gene expression.

[Expression of the third open reading frame of the drosophila MDG4 retrotransposon similar to the retroviral env-genes, occurring through splicing].

The presence of a third long open reading frame (ORF3) is the common feature of a number of Drosophila retrotransposons, including MDG4 (gypsy). Thus, these elements have a strong structural resemblance to the integrated forms of vertebrate retroviruses. To elucidate the mode of expression of ORF3, transcription analysis of MDG4 for several D.

Two Drosophila retrotransposon gypsy subfamilies differ in ability to produce new DNA copies via reverse transcription in Drosophila cultured cells.

Plasmid DNA constructs containing 5' end truncated retrotransposon gypsy were introduced into Drosophila cultured cells. Appearance of new complete DNA copies with reconstructed via reverse transcription 5'LTR were detected by PCR after transient expression and by Southern blot analysis of genome DNA of stably transformed cells. Two gypsy subfamilies supposed to be different in transpositional activity were analyzed in terms of their ability to produce new DNA copies via reverse transcription in D.

[Features of the structural organization of the MDG1 retrotransposon of Drosophila, revealed during its sequencing].

The two long open reading frames (ORF1 and ORF2) have been identified in the primary structure of the full-length copy of mdg1 Drosophila retrotransposon by the sequence analysis. These two partially overlapping frames code for the necessary information for transposition through the reverse transcription mechanism. There are unusually long leader and terminal regions in mdg1.