Insulin plays a crucial role in the regulation of glucose-homeostasis, and its synthesis is regulated by several stimuli. The transcription of the human insulin gene, enhanced by an elevated intracellular concentration of calcium ions, was completely blocked by Ca2+/calmodulin-dependent protein kinase inhibitor. The activity of the transcription factor activating transcription factor-2 (ATF-2), which binds to the cAMP responsive elements of the human insulin gene, was enhanced by Ca2+/calmodulin-dependent protein kinase IV (CaMKIV). Mutagenesis studies showed that Thr69, Thr71, and Thr73 of ATF-2 are all required for activation by CaMKIV. CaMKIV-induced ATF-2 transcriptional activity was not altered by activation of cJun NH2-terminal protein kinase (JNK) or p38 mitogen-activated protein (MAP) kinase. Furthermore, when transfected into rat primary cultured islets, ATF-2 enhanced glucose-induced insulin promoter activity, whereas cAMP response element-binding protein (CREB) repressed it. These results suggest a mechanism in which ATF-2 regulates insulin gene expression in pancreatic beta-cells, with the transcriptional activity of ATF-2 being increased by an elevated concentration of calcium ions.
Activating transcription factor-2 is a positive regulator in CaM kinase IV-induced human insulin gene expression.
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N Ban, Y Yamada, Y Someya, Y Ihara, T Adachi, A Kubota, R Watanabe, A Kuroe, A Inada, K Miyawaki, Y Sunaga, Z P Shen, T Iwakura, K Tsukiyama, S Toyokuni, K Tsuda, Y Seino; Activating transcription factor-2 is a positive regulator in CaM kinase IV-induced human insulin gene expression.. Diabetes 1 July 2000; 49 (7): 1142–1148. https://doi.org/10.2337/diabetes.49.7.1142
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