Interplay of the E Box, the Cyclic AMP Response Element, and HTF4/HEB in Transcriptional Regulation of the Neurospecific, Neurotrophin-InduciblevgfGene†

Abstract

vgf is a neurotrophin response-specific, developmentally regulated gene that codes for a neurosecretory polypeptide. Its transcription in neuronal cells is selectively activated by the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor, and neurotrophin 3, which induce survival and differentiation, and not by epidermal growth factor. We studied a short region of the rat vgf promoter which is essential for its regulated expression. A cyclic AMP response element (CRE) within this region is necessary for NGF induction of vgf transcription. Two sites upstream of CRE, an E box and a CCAAT sequence, bind nuclear protein complexes and are involved in transcriptional control. The E box has a dual role. It acts as an inhibitor in NIH 3T3 fibroblasts, together with a second E box located downstream, and as a stimulator in the NGF-responsive cell line PC12. By expression screening, we have isolated the cDNA for a basic helix-loop-helix transcription factor, a homolog of the HTF4/HEB E protein, that specifically binds the vgf promoter E box. The E protein was present in various cell lines, including PC12 cells, and was a component of a multiprotein nuclear complex that binds the promoter in vitro. The E box and CRE cooperate in binding to this complex, which may be an important determinant for neural cell-specific expression.

Proximal Promoter Sequences Mediate Cell-specific and Elevated Expression of the Favorable Prognosis Marker TrkA in Human Neuroblastoma Cells

“…Further, Egr-1 sites are involved in the regulation of certain neuronally expressed promoters, and this factor is expressed and inducible in neuroblastoma cells (55,56). ATF and AP2 family members also have an important role in neuronal gene expression (55,(57)(58)(59). Finally, ets domain proteins have been implicated in cell-specific gene expression and at least some members of this family are restricted to or enriched in neuronal cells, including PEA3 and NERF (55,60,61).…”

Interaction between the Skeletal Muscle Type 1 Na+Channel Promoter E-box and an Upstream Repressor Element

“…expressed in PC12 cells are regulated by interactions between E-boxes and separate regulatory sequences, and this interaction is mediated in part through bHLH proteins (24,25). We anticipate that there may be parallel mechanisms controlling expression of the SkM1 and RBII genes, with regulation by bHLH factors acting as a common theme.…”

NGF‐dependent and tissue‐specific transcription of vgf is regulated by a CREB–p300 and bHLH factor interaction

“…Cells were cultured as previously described [11,13]. NIH3T3 cells (3×10 5 cells/35 mm plate) and PC12 cells (3×10 6 cells) were transfected overnight by Lipofectamine (Gibco BRL).…”

“…By using as probe the whole 110 bp region, rather than short sequences containing a single protein binding site, we showed the presence of two protein complexes interacting with the vgf promoter in vitro. The C complex, neuro‐specific, strongly binds the CCAAT sequence, while the E–CRE complex, ubiquitous, interacts with E‐box and CRE sites [13].…”