Inada A, Someya Y, Yamada Y, Ihara Y, Kubota A, Ban N, Watanabe R, Tsuda K, Seino Y
Department of Metabolism and Clinical Nutrition, Graduate School of Medicine, Kyoto University, Kyoto, Japan 606-8507, USA.
J Biol Chem. 1999 Jul 23;274(30):21095-103. doi: 10.1074/jbc.274.30.21095.
We analyzed a mechanism of transcriptional regulation of the human insulin gene by cyclic AMP response element modulator (CREM) through four cyclic AMP response elements (CREs). We isolated two novel CREM isoforms (CREMDeltaQ1 and CREMDeltaQ2), which lack one of the glutamine-rich domains, Q1 and Q2 respectively, and six known isoforms (CREMtaualpha, CREMalpha, inducible cyclic AMP early repressor (ICER) I, ICER Igamma, CREM-17X, and CREM-17) from rat pancreatic islets and the RINm5F pancreatic beta-cell line. CREM isoforms functioned as efficient transcriptional activators or repressors to modulate insulin promoter activity by binding to all of the insulin CREs. The binding activity of repressors is higher than that of activators and suppressed not only basal activity but also activator-induced activities. Furthermore, CREM activator interacted directly with the transcription factor IID components hTAF(II)130 and TATA box-binding protein (TBP). These results suggest that the activation of the insulin gene transcription by CREM activator is mediated by not only direct binding to the CREs but also by recruiting transcription factor IID to the insulin promoter via its interaction with hTAF(II)130 and TBP. On the other hand, the CREM repressor ICER competitively interrupts the binding of the activators to CREs and does not interact with either TBP or hTAF(II)130; therefore, it might fail to stabilize the basal transcriptional machinery and repress transactivation.
我们分析了环磷腺苷反应元件调节因子（CREM）通过四个环磷腺苷反应元件（CRE）对人胰岛素基因进行转录调控的机制。我们从大鼠胰岛和RINm5F胰腺β细胞系中分离出两种新型CREM异构体（CREMDeltaQ1和CREMDeltaQ2），它们分别缺失富含谷氨酰胺的结构域Q1和Q2之一，以及六种已知异构体（CREMtaualpha、CREMalpha、诱导型环磷腺苷早期阻遏物（ICER）I、ICER Igamma、CREM-17X和CREM-17）。CREM异构体通过与所有胰岛素CRE结合，作为有效的转录激活剂或阻遏剂来调节胰岛素启动子活性。阻遏剂的结合活性高于激活剂，不仅抑制基础活性，还抑制激活剂诱导的活性。此外，CREM激活剂直接与转录因子IID成分hTAF(II)130和TATA盒结合蛋白（TBP）相互作用。这些结果表明，CREM激活剂对胰岛素基因转录的激活不仅通过直接结合CRE来介导，还通过与hTAF(II)130和TBP的相互作用将转录因子IID募集到胰岛素启动子上来介导。另一方面，CREM阻遏物ICER竞争性地阻断激活剂与CRE的结合，并且不与TBP或hTAF(II)130相互作用；因此，它可能无法稳定基础转录机制并抑制反式激活。
