DNA sequence analysis reveals extensive homologies of regions preceding hsp70 and αβ heat shock genes in Drosophila melanogaster

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Abstract
Two kinds of RNA are synthesized at the 87C1 chromosomal locus of D. melanogaster in response to heat shock. One of these codes for the major heat shock protein, hsp 70; the other, .alpha..beta. RNA, derives from tandemly repeated .alpha..beta. units consisting of adjacent .alpha. and .beta. DNA elements and has no identified translation product. Another DNA element, .gamma., flanks the 5'' ends of some .alpha..beta. units. The complete nucleotide sequence of the 617-base-pair .alpha. and the 733-base-pair .gamma. element as well as a portion of the longer .beta. element is reported. Sequence comparisons between the .gamma. element and the 2 hsp70 genes at 87C1 reveal that the 406 base pairs of .gamma. immediately upstream from the 5'' end of the .alpha..beta. unit exhibit 97.5% homology with the sequences at and upstream from the 5'' end of the hsp70 genes. A similar homology also exists between .gamma. and an hsp70 gene present at another heat shock locus, 87A7, which contains no .alpha..beta. units. The coordinate induction by heat shock of the hsp70 and .alpha..beta. genes may be a consequence of their homologous 5'' flanking sequences. This extraordinary degree of sequence conservation may stem from the recent transposition of .alpha..beta. DNA to the 87C1 locus, an event that brought .alpha..beta. sequences adjacent to, and under the regulation of, the hsp70 control element.