BRD4 orchestrates recruitment of pause-release factor P-TEFb and the pausing complex NELF/DSIF to coordinate transcription elongation of interferon stimulated genes

Thursday, October 11, 2012 — Poster Session IV
2:00 p.m. – 4:00 p.m.	Natcher Conference Center, Building 45	NICHD	TRANS-2

* FARE Award Winner

Authors

• M.C. Patel
• M. Debrosse
• M. Smith
• A. Dey
• W. Huynh
• Y. Sarai
• T.D. Heightman
• T. Tamura
• K. Ozato

Abstract

RNA polymerase II (Pol II) and the pausing complex, NELF and DSIF are detected near the transcription start site (TSS) of many active and silent genes. Active transcription starts when the pause-release factor, P-TEFb is recruited to initiate productive elongation. However, the mechanism of P-TEFb recruitment and regulation of NELF/DSIF during transcription is not fully understood. We investigated this question in interferon (IFN) stimulated transcription, focusing on BRD4, a BET family protein that interacts with P-TEFb. Besides P-TEFb, BRD4 binds to acetylated histones through the bromodomain. We show that BRD4 and P-TEFb were robustly recruited to IFN stimulated genes (ISGs) after stimulation. Likewise, NELF/DSIF was hardly detectable on ISGs prior to stimulation, but was strongly recruited after IFN treatment, indicating that NELF/DSIF has a role in elongation, but not pausing prior to ISG transcription. A shRNA-based knockdown of NELF revealed that it negatively regulates the passage of Pol II and DSIF across the ISGs during elongation, reducing total ISG transcript output. Analyses with a BRD4 small molecule inhibitor showed that IFN-induced recruitment of P-TEFb and NELF/DSIF was under control of BRD4. We suggest a model where BRD4 helps to coordinate positive and negative regulation of ISG elongation.

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