Figure 4. Pgc prevents P-TEFb recruitment.

a, Salivary gland polytene chromosome squashes prepared from third-instar larvae carrying either the sgs3-Gal4 driver alone or sgs3-Gal4 plus two copies of UAST-pgc ORF transgenes immunostained for pSer 5, CycT and Cdk9, and counter-stained with DAPI. Arrowheads indicate P-TEFb signals on cell debris in the Pgcexpressing salivary gland squash. b, Western blot analysis of salivary gland lysates from sgs3-Gal4 or sgs3-Gal4; 2×UAST-Pgc third-instar larvae. c, Real-time PCR analyses of ChIP experiments on the Hsp70 and Hsp27 gene regions in heatshocked (HS) or non-heat-shocked (NHS) S2 cell transfectants. The proportion of Pgc-expressing S2 cells after CuSO₄ induction was about 70%. Each result shows an average of at least three independent experiments with the standard error of the mean.