Breast Cancer Research and Treatment

, Volume 150, Issue 2, pp 265–278 | Cite as

Inhibition of BET proteins impairs estrogen-mediated growth and transcription in breast cancers by pausing RNA polymerase advancement

Preclinical Study


Estrogen (E2)-induced transcription requires coordinated recruitment of estrogen receptor α (ER) and multiple factors at the promoter of activated genes. However, the precise mechanism by which this complex stimulates the RNA polymerase II activity required to execute transcription is largely unresolved. We investigated the role of bromodomain (BRD) containing bromodomain and extra-terminal (BET) proteins, in E2-induced growth and gene activation. JQ1, a specific BET protein inhibitor, was used to block BET protein function in two different ER-positive breast cancer cell lines (MCF7 and T47D). Real-time PCR and ChIP assays were used to measure RNA expression and to detect recruitment of various factors on the genes, respectively. Protein levels were measured by Western blotting. JQ1 suppressed E2-induced growth and transcription in both MCF7 and T47D cells. The combination of E2 and JQ1 down-regulated the levels of ER protein in MCF7 cells but the loss of ER was not responsible for JQ1-mediated inhibition of E2 signaling. JQ1 did not disrupt E2-induced recruitment of ER and co-activator (SRC3) at the E2-responsive DNA elements. The E2-induced increase in histone acetylation was also not altered by JQ1. However, JQ1 blocked the E2-induced transition of RNA polymerase II from initiation to elongation by stalling it at the promoter region of the responsive genes upstream of the transcription start site. This study establishes BET proteins as the key mediators of E2-induced transcriptional activation. This adds another layer of complexity to the regulation of estrogen-induced gene activation that can potentially be targeted for therapeutic intervention.


Estrogen Transcription BET proteins JQ1 Estrogen receptor RNA polymerase II 



This work was supported by the Department of Defense Breast Program under Award number W81XWH-06-1-0590 Center of Excellence (VCJ), and in part by Dean’s Pilot Project Award 2014 (SS), Public Health Service Awards U54-CA149147 (RC), and the Lombardi Comprehensive Cancer Center Support Grant (CCSG) Core Grant NIH P30 CA051008. The views and opinions of the author(s) do not reflect those of the US Army or the Department of Defense.

Supplementary material

10549_2015_3319_MOESM1_ESM.pdf (427 kb)
Supplementary material 1 (PDF 428 kb)


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Copyright information

© Springer Science+Business Media New York 2015

Authors and Affiliations

  1. 1.Department of Oncology, Lombardi Comprehensive Cancer CenterGeorgetown University Medical CenterWashingtonUSA
  2. 2.Department of Breast Medical OncologyMD Anderson Cancer CenterHoustonUSA

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