The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.

<h4>Background</h4>Nrf1 (nuclear factor-erythroid 2 p45 subunit-related factor 1) is a transcription factor mediating cellular responses to xenobiotic and pro-oxidant stress. Nrf1 regulates the transcription of many stress-related genes through the electrophile response elements (EpREs)...

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Autores principales:	Nikolai L Chepelev, Joshua D Bennitz, Ting Huang, Skye McBride, William G Willmore
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2011
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/e6db0690b6f849baa8c9bca45a792be3
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spelling	oai:doaj.org-article:e6db0690b6f849baa8c9bca45a792be32021-11-18T07:31:42ZThe Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.1932-620310.1371/journal.pone.0029167https://doaj.org/article/e6db0690b6f849baa8c9bca45a792be32011-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/22216197/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>Nrf1 (nuclear factor-erythroid 2 p45 subunit-related factor 1) is a transcription factor mediating cellular responses to xenobiotic and pro-oxidant stress. Nrf1 regulates the transcription of many stress-related genes through the electrophile response elements (EpREs) located in their promoter regions. Despite its potential importance in human health, the mechanisms controlling Nrf1 have not been addressed fully.<h4>Principal findings</h4>We found that proteasomal inhibitors MG-132 and clasto-lactacystin-β-lactone stabilized the protein expression of full-length Nrf1 in both COS7 and WFF2002 cells. Concomitantly, proteasomal inhibition decreased the expression of a smaller, N-terminal Nrf1 fragment, with an approximate molecular weight of 23 kDa. The EpRE-luciferase reporter assays revealed that proteasomal inhibition markedly inhibited the Nrf1 transactivational activity. These results support earlier hypotheses that the 26 S proteasome processes Nrf1 into its active form by removing its inhibitory N-terminal domain anchoring Nrf1 to the endoplasmic reticulum. Immunoprecipitation demonstrated that Nrf1 is ubiquitinated and that proteasomal inhibition increased the degree of Nrf1 ubiquitination. Furthermore, Nrf1 protein had a half-life of approximately 5 hours in COS7 cells. In contrast, hypoxia (1% O(2)) significantly increased the luciferase reporter activity of exogenous Nrf1 protein, while decreasing the protein expression of p65, a shorter form of Nrf1, known to act as a repressor of EpRE-controlled gene expression. Finally, the protein phosphatase inhibitor okadaic acid activated Nrf1 reporter activity, while the latter was repressed by the PKC inhibitor staurosporine.<h4>Conclusions</h4>Collectively, our data suggests that Nrf1 is controlled by several post-translational mechanisms, including ubiquitination, proteolytic processing and proteasomal-mediated degradation as well as by its phosphorylation status.Nikolai L ChepelevJoshua D BennitzTing HuangSkye McBrideWilliam G WillmorePublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 6, Iss 12, p e29167 (2011)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Nikolai L Chepelev Joshua D Bennitz Ting Huang Skye McBride William G Willmore The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
description	<h4>Background</h4>Nrf1 (nuclear factor-erythroid 2 p45 subunit-related factor 1) is a transcription factor mediating cellular responses to xenobiotic and pro-oxidant stress. Nrf1 regulates the transcription of many stress-related genes through the electrophile response elements (EpREs) located in their promoter regions. Despite its potential importance in human health, the mechanisms controlling Nrf1 have not been addressed fully.<h4>Principal findings</h4>We found that proteasomal inhibitors MG-132 and clasto-lactacystin-β-lactone stabilized the protein expression of full-length Nrf1 in both COS7 and WFF2002 cells. Concomitantly, proteasomal inhibition decreased the expression of a smaller, N-terminal Nrf1 fragment, with an approximate molecular weight of 23 kDa. The EpRE-luciferase reporter assays revealed that proteasomal inhibition markedly inhibited the Nrf1 transactivational activity. These results support earlier hypotheses that the 26 S proteasome processes Nrf1 into its active form by removing its inhibitory N-terminal domain anchoring Nrf1 to the endoplasmic reticulum. Immunoprecipitation demonstrated that Nrf1 is ubiquitinated and that proteasomal inhibition increased the degree of Nrf1 ubiquitination. Furthermore, Nrf1 protein had a half-life of approximately 5 hours in COS7 cells. In contrast, hypoxia (1% O(2)) significantly increased the luciferase reporter activity of exogenous Nrf1 protein, while decreasing the protein expression of p65, a shorter form of Nrf1, known to act as a repressor of EpRE-controlled gene expression. Finally, the protein phosphatase inhibitor okadaic acid activated Nrf1 reporter activity, while the latter was repressed by the PKC inhibitor staurosporine.<h4>Conclusions</h4>Collectively, our data suggests that Nrf1 is controlled by several post-translational mechanisms, including ubiquitination, proteolytic processing and proteasomal-mediated degradation as well as by its phosphorylation status.
format	article
author	Nikolai L Chepelev Joshua D Bennitz Ting Huang Skye McBride William G Willmore
author_facet	Nikolai L Chepelev Joshua D Bennitz Ting Huang Skye McBride William G Willmore
author_sort	Nikolai L Chepelev
title	The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
title_short	The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
title_full	The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
title_fullStr	The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
title_full_unstemmed	The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.
title_sort	nrf1 cnc-bzip protein is regulated by the proteasome and activated by hypoxia.
publisher	Public Library of Science (PLoS)
publishDate	2011
url	https://doaj.org/article/e6db0690b6f849baa8c9bca45a792be3
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The Nrf1 CNC-bZIP protein is regulated by the proteasome and activated by hypoxia.

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