Chen Yili, Lin Grace, Huo Jeffrey S, Barney Deborah, Wang Zhenni, Livshiz Tamara, States David J, Qin Zhaohui S, Schwartz Jessica
Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109-5622.
Endocrinology. 2009 Aug;150(8):3645-54. doi: 10.1210/en.2009-0212. Epub 2009 Apr 30.
For insight into transcriptional mechanisms mediating physiological responses to GH, data mining was performed on a profile of GH-regulated genes induced or inhibited at different times in highly responsive 3T3-F442A adipocytes. Gene set enrichment analysis indicated that GH-regulated genes are enriched in pathways including phosphoinositide and insulin signaling and suggested that suppressor of cytokine signaling 2 (SOCS2) and phosphoinositide 3' kinase regulatory subunit p85alpha (Pik3r1) are important targets. Model-based Chinese restaurant clustering identified a group of genes highly regulated by GH at times consistent with its key physiological actions. This cluster included IGF-I, phosphoinositide 3' kinase p85alpha, SOCS2, and cytokine-inducible SH2-containing protein. It also contains the most strongly repressed gene in the profile, B cell lymphoma 6 (Bcl6), a transcriptional repressor. Quantitative real-time PCR verified the strong decrease in Bcl6 mRNA after GH treatment and induction of the other genes in the cluster. Transcriptional network analysis of the genes implicated signal transducer and activator of transcription (Stat) 5 as hub regulating the most responsive genes, Igf1, Socs2, Cish, and Bcl6. Transcriptional activation analysis demonstrated that Bcl6 inhibits SOCS2-luciferase and blunts its stimulation by GH. Occupancy of endogenous Bcl6 on SOCS2 DNA decreased after GH treatment, whereas occupancy of Stat5 increased concomitantly. Thus, GH-mediated inhibition of Bcl6 expression may reverse the repression of SOCS2 and facilitate SOCS2 activation by GH. Together these analyses identify Bcl6 as a participant in GH-regulated gene expression and suggest an interplay between the repressor Bcl6 and the activator Stat5 in regulating genes, which contribute to GH responses.
为深入了解介导生长激素（GH）生理反应的转录机制，我们对高反应性3T3 - F442A脂肪细胞在不同时间诱导或抑制的GH调节基因谱进行了数据挖掘。基因集富集分析表明，GH调节基因在包括磷酸肌醇和胰岛素信号传导的途径中富集，并表明细胞因子信号传导抑制因子2（SOCS2）和磷酸肌醇3'激酶调节亚基p85α（Pik3r1）是重要靶点。基于模型的中餐厅聚类识别出一组在与GH关键生理作用一致的时间受到高度调节的基因。该聚类包括胰岛素样生长因子I（IGF - I）、磷酸肌醇3'激酶p85α、SOCS2和细胞因子诱导含SH2蛋白。它还包含该谱中抑制最强的基因，即转录抑制因子B细胞淋巴瘤6（Bcl6）。定量实时PCR验证了GH处理后Bcl6 mRNA的强烈下降以及聚类中其他基因的诱导。对这些基因的转录网络分析表明，信号转导和转录激活因子（Stat）5作为枢纽调节最敏感的基因，即Igf1、Socs2、Cish和Bcl6。转录激活分析表明，Bcl6抑制SOCS2 - 荧光素酶并减弱GH对其的刺激。GH处理后内源性Bcl6在SOCS2 DNA上的占有率降低，而Stat5的占有率随之增加。因此，GH介导的Bcl6表达抑制可能会逆转对SOCS2的抑制，并促进GH对SOCS2的激活。这些分析共同确定Bcl6是GH调节基因表达的参与者，并表明抑制因子Bcl6和激活因子Stat5在调节对GH反应有贡献的基因中存在相互作用。
