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Transcriptional and post-translational regulation of mouse cation transport regulator homolog 1

Kentaro Oh-Hashi1, Yuki Nomura, Kiyo Shimada

  • 1Department of Biomolecular Science, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan. oohashi@gifu-u.ac.jp

Molecular and Cellular Biochemistry
|April 26, 2013
PubMed

Insights

Cation transport regulator homolog 1 (Chac1) is induced by endoplasmic reticulum stress via transcriptional and post-translational mechanisms in neuronal cells. This study elucidates Chac1 promoter activity and its regulation by ATF4 and proteasome degradation.

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Neuroscience

Background:

  • Cation transport regulator homolog 1 (Chac1) is a novel pro-apoptotic factor implicated in endoplasmic reticulum (ER) stress.
  • The transcriptional regulation of Chac1, particularly its promoter function, remains poorly understood.
  • The role of activating transcription factor 4 (ATF4) in Chac1 gene expression is suggested but not fully characterized.

Purpose of the Study:

  • To characterize the promoter activity of the mouse Chac1 gene under ER stress conditions.
  • To investigate the transcriptional regulation of Chac1 by ER stress sensors and transcription factors.
  • To elucidate the post-translational regulation of Chac1 protein expression in neuronal cells.

Main Methods:

  • Neuro2a cells were treated with ER stress inducers like thapsigargin (Tg), tunicamycin (Tm), and brefeldin A.
  • Chac1 mRNA expression was analyzed using DNA array analysis and RT-PCR.
  • Mouse Chac1 promoter activity was assessed via luciferase reporter assays with site-directed mutagenesis.
  • Chac1 protein expression was examined in the presence of the proteasome inhibitor MG132.

Main Results:

  • Chac1 mRNA expression was significantly induced by Tg, Tm, and brefeldin A in Neuro2a cells.
  • The CREB/ATF element and amino acid response element in the Chac1 promoter were found to be functional and responsive to Tm and ATF4.
  • Dual mutations in these promoter elements drastically reduced basal activity and ER stress-induced responses.
  • Chac1 protein expression was observed only when proteasome activity was inhibited by MG132, despite transient gene overexpression.

Conclusions:

  • The study provides the first detailed characterization of the mouse Chac1 promoter, identifying key regulatory elements responsive to ER stress.
  • Both transcriptional activation, involving ATF4 and specific promoter elements, and post-translational regulation via the proteasome are critical for Chac1 expression in neuronal cells.
  • These findings reveal a dual regulatory mechanism controlling Chac1 levels during ER stress in a neuronal context.

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