Genomic organization and transcription of the αβ heat shock DNA in Drosophila melanogaster

Abstract

Previous studies have shown that (i) several RNAs induced by heat shock of Drosophila melanogaster cells are homologous to tandemly repeated αβ units found in cloned segments of D. melanogaster DNA, and (ii) the αβ sequences are present both at a major heat shock locus, 87C1, and the chromocenter of polytene chromosomes (Lis, J.T., Prestidge, L. and Hogness, D.S. [1978] Cell 14, 901-919). We have used deficiencies that delete DNA from the 87C region to examine the arrangement of αβ sequences at this locus and in the centromeric heterochromatin that comprises the chromocenter, and also to determine the chromosomal location of the induced transcription. The tandemly repeated αβ units are restricted to the 87C locus. In contrast, the chromocentral αβ sequences do not form intact αβ units, and are dispersed at heterochromatic sites in some other form. Although only half of the αβ DNA is at the 87c locus, essentially all αβ transcripts (>99.5%) are derived from this locus. © 1981 IRL Press Limited.