Bcl-2 Transcription from the Proximal P2 Promoter Is Activated in Neuronal Cells by the Brn-3a POU Family Transcription Factor

Martin D Smith,Elizabeth A Ensor,Robert S Coffin,Linda M Boxer,David S Latchman

doi:10.1074/jbc.273.27.16715

Martin D Smith, Elizabeth A Ensor + Show 3 more

Open Access

https://doi.org/10.1074/jbc.273.27.16715

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Abstract

The BCL-2 protein is able to protect neuronal and other cell types from apoptotic programmed cell death and plays a key role in regulating the rate of apoptosis during development of the nervous system. We have previously demonstrated that the Brn-3a POU domain transcription factor protects sensory neurons from apoptotic programmed cell death induced by nerve growth factor withdrawal. We report here that Bcl-2 transcription is predominantly initiated from the Bcl-2 P2 promoter in both the ND7 neuronal cell line and primary dorsal root ganglion neurons, in contrast to the predominant use of the Bcl-2 P1 promoter in other cell types. Moreover, Bcl-2 transcription initiated from the P2 region increases in ND7 cells stably overexpressing Brn-3a, resulting in enhanced BCL-2 protein levels. Similarly, the Bcl-2 P2 promoter is directly activated by Brn-3a in co-transfection assays in both ND7 cells and dorsal root ganglion neurons. Analysis of the Bcl-2 regulatory sequence revealed a binding site for Brn-3a that is required for maximal activation by Brn-3a both in transfected cells and during differentiation of ND7 cells. Together these data identify Brn-3a as the first transcription factor regulating Bcl-2 activity specifically in neuronal cells and indicate that the anti-apoptotic effect of Brn-3a is likely to be mediated, at least in part, via the up-regulation of Bcl-2 expression.

Highlights

The BCL-2 protein is able to protect neuronal and other cell types from apoptotic programmed cell death and plays a key role in regulating the rate of apoptosis during development of the nervous system
Brn-3a Enhances Expression of Bcl-2 but Not Bad, Bax, or Bcl-x in ND7 Cells—We have recently described the ability of transfected Brn-3a to confer protection against apoptosis in ND7 cells following serum removal, as well as in primary cultures of nerve growth factor (NGF)-dependent sensory neurons following the removal of NGF from culture media
We first wished to determine the precise nature of Bcl-2 transcription in neuronal cells as this has yet to be documented in the literature

Summary

Introduction

The BCL-2 protein is able to protect neuronal and other cell types from apoptotic programmed cell death and plays a key role in regulating the rate of apoptosis during development of the nervous system. The three members of the Brn-3 family of type IV POU domain transcription factors, Brn-3a [23,24,25], Brn-3b [25], and Brn-3c [24, 26], are expressed in distinct but overlapping sets of neurons in the developing and adult nervous systems [26, 27] suggesting that, like the highly homologous nematode Unc-86 POU factor, they may play a key role in the regulation of gene expression in neuronal cells

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