Bromodomain and Extraterminal Inhibition by JQ1 Produces Divergent Transcriptional Regulation of Suppressors of Cytokine Signaling Genes in Adipocytes
Bromodomain and Extraterminal Inhibition by JQ1 Produces Divergent Transcriptional Regulation of Suppressors of Cytokine Signaling Genes in Adipocytes
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DOI：
10.1210/endocr/bqz034
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发表时间：
2020-02-01
期刊：
影响因子：
4.8
通讯作者：
Stephens, Jacqueline M.
中科院分区：
文献类型：
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作者：
de Sa, Paula Mota;Richard, Allison J.;Stephens, Jacqueline M.
Janus激酶信号转导和转录激活因子（JAK-STAT）信号通路具有细胞特异性功能。细胞因子信号传导抑制因子（SOCS）蛋白是JAK-STAT信号传导的负反馈调节因子。STAT 5在脂肪细胞发育和功能中起重要作用，并且溴结构域和末端外（BET）蛋白可能参与STAT 5的转录活性。我们用BET抑制剂JQ 1处理3 T3-L1脂肪细胞，并观察到生长激素（GH）诱导的来自SOCS家族的2个STAT 5靶基因Socs 3和Cish的表达通过BET抑制被反向调节（分别增加和减少）。染色质免疫沉淀分析显示，STAT 5结合的变化与基因表达变化无关。GH促进BET蛋白BRD 2向Cish启动子的募集，但不促进Socs 3启动子的募集。JQ 1治疗消除了这种效应以及GH诱导的核糖核酸聚合酶II（RNA Pol II）与Cish转录起始位点的结合。BRD 2敲除还抑制GH对Cish的诱导，进一步支持BRD 2在Cish转录激活中的作用。相反，JQ 1增加了激活的Pol II与Socs 3编码区的结合，表明增强了信使RNA（mRNA）的延伸。我们发现JQ 1瞬时降低了正转录延伸因子（P-TEFb）与其抑制剂双乙酰胺诱导型1（HEXIM 1）之间的相互作用，这与先前描述的JQ 1的脱靶效应一致，由此P-TEFb变得更容易被不依赖BET蛋白激活转录的基因招募。这些结果表明，Socs 3和Cish的转录调控有很大的不同，并表明这2个密切相关的蛋白质在脂肪细胞中的不同作用。
The Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway has cell-specific functions. Suppressors of cytokine signaling (SOCS) proteins are negative-feedback regulators of JAK-STAT signaling. STAT5 plays a significant role in adipocyte development and function, and bromodomain and extraterminal (BET) proteins may be involved in STAT5 transcriptional activity. We treated 3T3-L1 adipocytes with the BET inhibitor JQ1 and observed that growth hormone (GH)-induced expression of 2 STAT5 target genes from the SOCS family, Socs3 and Cish, were inversely regulated (increased and decreased, respectively) by BET inhibition. Chromatin immunoprecipitation analyses revealed that changes in STAT5 binding did not correlate with gene expression changes. GH promoted the recruitment of the BET protein BRD2 to the Cish, but not Socs3, promoter. JQ1 treatment ablated this effect as well as the GH-induced binding of ribonucleic acid polymerase II (RNA Pol II) to the Cish transcription start site. BRD2 knockdown also suppressed GH induction of Cish, further supporting the role of BRD2 in Cish transcriptional activation. In contrast, JQ1 increased the binding of activated Pol II to the Socs3 coding region, suggesting enhanced messenger RNA (mRNA) elongation. Our finding that JQ1 transiently reduced the interaction between the positive transcription elongation factor (P-TEFb) and its inhibitor hexamethylene bis-acetamide inducible 1 (HEXIM1) is consistent with a previously described off-target effect of JQ1, whereby P-TEFb becomes more available to be recruited by genes that do not depend on BET proteins for activating transcription. These results demonstrate substantially different transcriptional regulation of Socs3 and Cish and suggest distinct roles in adipocytes for these 2 closely related proteins.