Identification of the promoter region and the 5′-untranslated exons of the human voltage-gated sodium channel Nav1.1 gene (SCN1A) and enhancement of gene expression by the 5′-untranslated exons

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Abstract

Voltage-gated sodium channels play critical roles in the excitability of the brain. A decreased level of Nav1.1 has been identified as the cause of severe myoclonic epilepsy in infancy. In the present study, we identified the transcription start site and three 5′-untranslated exons of SCN1A by using 5′-full RACE. The 2.5-kb region upstream of the transcription start site was targeted as a potential location of the promoter. The 2.5-kb genomic fragment (P2.5, from +26 to –2,500) and the 2.7-kb fragment (P2.7, P2.5 combined with the 227-bp 5′-untranslated exons) were cloned to produce luciferase constructs. The P2.5 and the P2.7 drove luciferase gene expression in the human neuroblastoma cell line SH-SY5Y but not in the human embryonic kidney cell line HEK-293. The 5′-untranslated exons could greatly enhance gene expression in SH-SY5Y cells. The P2.7 could be used as a functional unit to study the role of SCN1A noncoding sequences in gene expression. These findings will also help in exploring the possibility of promoter mutant-induced diseases and revealing the mechanism underlying the regulation of SCN1A expression in the normal brain. © 2008 Wiley-Liss, Inc.

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