Regulation of Transcription Elongation by the Super Elongation Complex

Open Access
Campbell, Katie Marie
Area of Honors:
Biochemistry and Molecular Biology
Bachelor of Science
Document Type:
Thesis Supervisors:
  • David Scott Gilmour, Thesis Supervisor
  • Benjamin Franklin Pugh, Honors Advisor
  • Richard John Frisque, Faculty Reader
  • transcription
  • elongation
  • regulation
  • RNA polymerase II
  • Super Elongation Complex
Understanding the regulation of gene transcription allows us to better analyze gene activity and function. Using Drosophila as a model system, I am studying the function of specific proteins involved in the transcriptional elongation control checkpoint. Normally, RNA polymerase II is paused at the promoters of hsp70 genes, repressed by negative elongation factors. Positive transcription elongation factor, P-TEFb, is thought to reactivate RNA polymerase II from its paused state in order to allow transcription to occur. P-TEFb associates with ELL and Lilli in the Super Elongation Complex. To investigate the role of these proteins in transcription of hsp70, I used RNA interference to deplete P-TEFb, ELL, and Lilli to monitor the effects on the expression of an hsp70 reporter gene. Depletion of these proteins resulted in marked inhibition of the hsp70 reporter gene. To assess if this inhibition was due to defects in Pol II behavior, I analyzed the association of Pol II with hsp70 in polytene chromosomes derived from the salivary glands of heat shocked larvae. P-TEFb-depleted glands were not amenable to this immunofluorescence analysis because they were too small. ELL- and Lilli- depleted glands did not exhibit any obvious changes in Pol II levels at hsp70, but exhibited a striking loss of phosphorylation of serine 2 in the carboxyl terminal domain of the largest subunit of Pol II. Phosphorylation of serine 2 in the CTD of Pol II has been correlated with the activation of the paused Pol II, but my results suggest that it is not essential for activation of the paused Pol II at the hsp70 gene.