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5′UTR of the neurogenic bHLH Nex1/MATH‐2/NeuroD6 gene is regulated by two distinct promoters through CRE and C/EBP binding sites
Author(s) -
Uittenbogaard Martine,
Martinka Debra L.,
Johnson Peter F.,
Vinson Charles,
Chiaramello Anne
Publication year - 2007
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.21093
Subject(s) - promoter , biology , transcription factor , enhancer , locus control region , exon , microbiology and biotechnology , response element , gene , untranslated region , regulation of gene expression , reporter gene , gene expression , genetics , messenger rna
Expression of the bHLH transcription factor Nex1/MATH‐2/NeuroD6, a member of the NeuroD subfamily, parallels overt neuronal differentiation and synaptogenesis during brain development. Our previous studies have shown that Nex1 is a critical effector of the NGF pathway and promotes neuronal differentiation and survival of PC12 cells in the absence of growth factors. In this study, we investigated the transcriptional regulation of the Nex1 gene during NGF‐induced neuronal differentiation. We found that Nex1 expression is under the control of two conserved promoters, Nex1‐P1 and Nex1‐P2, located in two distinct non‐coding exons. Both promoters are TATA‐less with multiple transcription start sites, and are activated on NGF or cAMP exposure. Luciferase‐reporter assays showed that the Nex1‐P2 promoter activity is stronger than the Nex1‐P1 promoter activity, which supports the previously reported differential expression levels of Nex1 transcripts throughout brain development. Using a combination of DNaseI footprinting, EMSA assays, and site‐directed mutagenesis, we identified the essential regulatory elements within the first 2 kb of the Nex1 5′UTR. The Nex1‐P1 promoter is mainly regulated by a conserved CRE element, whereas the Nex1‐P2 promoter is under the control of a conserved C/EBP binding site. Overexpression of wild‐type C/EBPβ resulted in increased Nex1‐P2 promoter activity in NGF‐differentiated PC12 cells. The fact that Nex1 is a target gene of C/EBPβ provides new insight into the C/EBP transcriptional cascade known to promote neurogenesis, while repressing gliogenesis. © 2006 Wiley‐Liss, Inc.