Fig. 3. JIL-1 is not upregulated at actively transcribed regions during the heat shock response. (A) Polytene chromosome squash preparations from wild-type Drosophila larvae (wt) triple labeled with Pol IIo^ser2 antibody (green), JIL-1 mAb 5C9 (red), and Hoechst (DNA, gray/blue), with (right column) and without (left column) heat shock treatment. At many sites that showed especially high levels of Pol IIo^ser2 staining, such as at developmental puffs, there were relatively low levels of JIL-1 (arrow). After heat shock treatment, Pol IIo^ser2 labeling was reduced at most sites while being dramatically upregulated at heat shock-induced puffs (boxed area), whereas there was no discernable redistribution of JIL-1. (B) Higher magnification of the boxed area from A, showing that there was no upregulation of JIL-1 at the 87A/C and 93D heat shock puffs (boxed).