The uninduced Drosophila hsp70 gene is poised for rapid activation. Here we 
examine the rapid changes upon heat shock in levels and location of heat shock 
factor (HSF), RNA polymerase II (Pol II) and its phosphorylated forms, and the 
Pol II kinase P-TEFb on hsp70 in vivo by using both real-time PCR assays of 
chromatin immunoprecipitates and polytene chromosome immunofluorescence. These 
studies capture Pol II recruitment and progression along hsp70 and reveal 
distinct spatial and temporal patterns of serine 2 and serine 5 phosphorylation: 
in uninduced cells, the promoter-paused Pol II shows Ser5 but not Ser2 
phosphorylation, and in induced cells the relative level of Ser2-P Pol II is 
lower at the promoter than at regions downstream. An early time point of heat 
shock activation captures unphosphorylated Pol II recruited to the promoter 
prior to P-TEFb, and during the first wave of transcription Pol II and the 
P-TEFb kinase can be seen tracking together across hsp70 with indistinguishable 
kinetics. Pol II distributions on several other genes with paused Pol II show a 
pattern of Ser5 and Ser2 phosphorylation similar to that of hsp70. These studies 
of factor choreography set important limits in modeling transcription regulatory 
mechanisms.