Tao Cai1, Hiroki Hirai, Huanyu Xu, Abner L Notkins. 1. Experimental Medicine Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research (NIDCR), National Institutes of Health (NIH), B30/Rm106, Bethesda, MD, 20892, USA, tcai@mail.nih.gov.
Abstract
AIMS: IA-2 is a transmembrane protein found in the dense-core vesicles (DCV) of neuroendocrine cells and one of the major autoantigens in type 1 diabetes. DCV are involved in the secretion of hormones (e.g., insulin) and neurotransmitters. Stimulation of pancreatic β cells with glucose upregulates the expression of IA-2 and an increase in IA-2 results in an increase in the number of DCV. Little is known, however, about the promoter region of IA-2 or the transcriptional factors that regulate the expression of this gene. METHODS: In the present study, we constructed eight deletion fragments from the upstream region of the IA-2 transcription start site and linked them to a luciferase reporter. RESULTS: By this approach, we have identified a short bp region (-216 to +115) that has strong promoter activity. We also identified a transcription factor, cAMP responsive element-binding protein (CREB), which binds to two CREB-related binding sites located in this region. The binding of CREB to these sites enhanced IA-2 transcription by more than fivefold. We confirmed these findings by site-directed mutagenesis, chromatin immunoprecipitation assays and RNAi inhibition. CONCLUSION: Based on these findings, we conclude that the PKA pathway is a critical, but not the exclusive signaling pathway involved in IA-2 gene expression.
AIMS: IA-2 is a transmembrane protein found in the dense-core vesicles (DCV) of neuroendocrine cells and one of the major autoantigens in type 1 diabetes. DCV are involved in the secretion of hormones (e.g., insulin) and neurotransmitters. Stimulation of pancreatic β cells with glucose upregulates the expression of IA-2 and an increase in IA-2 results in an increase in the number of DCV. Little is known, however, about the promoter region of IA-2 or the transcriptional factors that regulate the expression of this gene. METHODS: In the present study, we constructed eight deletion fragments from the upstream region of the IA-2 transcription start site and linked them to a luciferase reporter. RESULTS: By this approach, we have identified a short bp region (-216 to +115) that has strong promoter activity. We also identified a transcription factor, cAMP responsive element-binding protein (CREB), which binds to two CREB-related binding sites located in this region. The binding of CREB to these sites enhanced IA-2 transcription by more than fivefold. We confirmed these findings by site-directed mutagenesis, chromatin immunoprecipitation assays and RNAi inhibition. CONCLUSION: Based on these findings, we conclude that the PKA pathway is a critical, but not the exclusive signaling pathway involved in IA-2 gene expression.
Authors: Melanie J Luther; Astrid Hauge-Evans; Kleber L A Souza; Anne Jörns; Sigurd Lenzen; Shanta J Persaud; Peter M Jones Journal: Biochem Biophys Res Commun Date: 2006-02-10 Impact factor: 3.575
Authors: Deidre Jansson; Andy Cheuk-Him Ng; Accalia Fu; Chantal Depatie; Mufida Al Azzabi; Robert A Screaton Journal: Proc Natl Acad Sci U S A Date: 2008-07-14 Impact factor: 11.205