THE DROSOPHILA-MICROPIA RETROTRANSPOSON ENCODES A TESTIS-SPECIFIC ANTISENSE RNA COMPLEMENTARY TO REVERSE-TRANSCRIPTASE

The micropia transposable element of Drosaphila hydei is a long termin al repeat-containing retrotransposon present in both the autosomes and the Y chromosome. micropia expression gives rise to a complex set of sense and antisense RNAs transcribed primarily during spermatogenesis. The most abundant sense RNAs constitute an assortment of heterogeneou s high-molecular-weight transcripts expressed as constituents of the Y -chromosomal lampbrush loops of primary spermatocytes. In addition, mi cropia encodes a full-length RNA that extends between the two long ter minal repeats of the element. The major l.O-kb antisense RNA character ized is complementary to the reverse transcriptase and RNase H coding regions of micropia, It is expressed from a testis-specific promoter d uring the primary spermatocyte stages and is detectable until spermati d elongation stages. Sequence comparison of this promoter with the 5' region of other testis-specific genes allows the conception of a conse rved sequence that is responsible for this pattern of expression. A 28 4-bp fragment containing this sequence is able to drive testis-specifi c expression of the Escherichia coli lacZ gene in Drosophila melanogas ter. This sequence is conserved in the micropia elements present in ot her Drosophila species that also encode an antisense RNA. The evolutio nary conservation of micropia antisense RNA expression and the sequenc es responsible for its testis-specific transcription suggests a role f or this antisense RNA in the control of germ line expression of the fu ll-length transcript or transposon-encoded proteins.