Biopolymers and cell. 1989. Volume 5. № 3. 5 - 22

I. S. Gubenko

«UNUSUAL» LOCI OF DROSOPHILA GENOME ACTIVATED BY HEAT SHOCK AND OTHER STRESS CONDITIONS (A REVIEW)

Summary

    The 93D heat-shock (hs) locus differs fundamentally from the other well characterized protein-coding hs loci of D. melanogaster. Despite a high level of RNA production, 93D appears to code no major hs proteins (hsp's) whose genes are mapped in other large hs puffs. A major, 53D-like, puff with the unusual inducibility characteristics and specific structural and functional features is a component of the hs response in every Drosophila species studied. DNA from «unusual» hs loci of 93D D. melanogaster and 2-48B D. hydei is cloned and characterized. The unique and neighbouring repetitive DNA sequences of the loci are transcribed, but these transcripts would probably contain no coding sequences. The ultrastructural features of such loci show considerable evolutionary conservation: 93D D. melanogaster, 2-48B D. hydei and 20CD D. virilis hs puffs contain giant RNP-par-ticles with specific antigenic determinants which are absent in other typical hs puffs. In contrast, the sequence composition of the «unusual» hs loci evolves much faster than the sequences coding the major hsp's. Unusual characteristics of the unique hs puffs permit suggesting that the function of these loci is conservative in spite of divergence at the nucleotide sequence level.