Deletion mapping of two D. melanogaster loci that code for the 70,000 dalton heat-induced protein.

Using deficiencies in D. melanogaster that lack either the 87A or 87C heat-induced puffs, we have shown that the 70,000 dalton heat-induced protein (hsp 70) is encoded at both these loci. Embryos deleted for one of the two loci retain the ability to make hsp 70 after heat shock, but deleting both loci eliminates synthesis of hsp 70. Thus both loci encode hsp 70 and can be active following heat shock. We have analyzed the proteins made by embryos lacking either 87A or 87C, and have compared the 87A- and 87C-coded hsp 70 by isoelectric focusing and tryptic peptide fingerprinting. The hsp 70 made by the two loci is very similar, although a variant tryptic peptide appears to be encoded only at 87C. Using deficiencies with slightly different breakpoints, we have mapped the 87A locus to band 87A7, the site of the 87A heat-induced puff. The 87C locus maps within 87C1.