The heat shock protein hsp70 binds in vivo to subregions 2-48BC and 3-58D of the polytene chromosomes of Drosophila hydei.

Multiple interactions of members of the hsp70 family with cellular components have already been described. We present, however, the first evidence that upon heat shock treatment hsp70 molecules interact with specific chromosomal subdivisions of the polytene chromosomes of Drosophila hydei. After a heat shock treatment of 20 min the protein binds to subdivision 3-58D1 and to the heat shock inducible subdivisions 2-48B3-6 and 2-48C1-2. Hsp70 molecules were also observed in subdivision 3-58D1 during recovery at 25 degrees C but not in subdivisions 2-48B3-6 and 2-48C1-2. Our data suggest that this interaction is stress specific. DNase and RNase experiments suggest, moreover, that the hsp70 molecules bind to RNA from ribonucleoproteins (RNPs) in subdivisions 2-48B3-6 and 2-48C1-2 and to DNA in subdivision 3-58D1. The DNA sequences in subdivision 3-58D1 seem to have the potential to adopt the Z-DNA conformation.