Histochemical localization of reverse transcriptase in polytene chromosomes of chironomids

The localization of a reverse transcriptase-related protein in salivary gla nd polytene chromosomes was investigated by immunohistochemistry in two spe cies of Chironomus. The antibodies used were raised against a recombinant p rotein containing phylogenetically conserved motifs of reverse transcriptas es and derived from an abundant non-LTR element previously identified in Ch ironomus. Immunoreactive protein was found in some telomeres, in a centrome ric region, in a few interstitial bands and in Balbiani ring 3. The telomer ic signal was probably dependent on transcription and increased dramaticall y when telomeric heat shock puffs were induced. A correlation with transcri ption was also seen in Balbiani ring 3, the immunobinding of which disappea red after inhibition of transcription with actinomycin D.