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Expression of Heme Oxygenase-1 in Response to Proteasomal Inhibition

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Heme oxygenase-1 (HO-1) is an antioxidant, antiapoptotic and cytoprotective enzyme, catalysing the degradation of heme to carbon monoxide, biliverdin and ferrous iron. Recent studies indicated that expression of HO-1 is under the control of proapoptotic transcription factor p53 and antioxidant transcription factor Nrf2. Whether each of these transcription factors act independently or there is a cooperation between them in inducing HO-1 expression remains to be elucidated. In this study, we examined the expression of HO-1 in B16F10 melanoma and 4T1 breast cancer cells after cell exposure to proteasome inhibitors. We found that HO-1 protein level is increased by about 70% in p53-wt B16F10 cells in response to proteasome inhibitor MG132 after 6 h. Likewise, a 6.8 fold increase in HO-1 level was observed after cell exposure to the highly specific proteasome inhibitor bortezomib after 6 h of treatment in B16F10 cells. Whereas no induction of HO-1 was observed in p53-null 4T1 cells after treatment with bortezomib for 6 h. Next, we aligned HO-1 untranslated region with a consensus p53-responsive element. This bioinformatic analysis identified a p53-responsive element within the untranslated region of HO-1. Then, we examined HO-1 expression after a prolonged exposure to bortezomib in both B16F10 and 4T1 cell. These analyses similarly indicated that HO-1 is strongly induced in B16F10 cells in a dosedependent; contrary to our expectations, a strong induction of HO-1 is also observed in 4T1 cells. Therefore, it is concluded that HO-1 expression is under the control of p53 during early time points of proteasomal inhibition. However, during prolonged incubation with proteasome inhibitors, HO-1 expression can be induced in a p53-independent manner, suggesting participation of other protein(s) with longer half-lives.
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Keywords: 4T1; B16F10; Bortezomib; HO-1; antioxidant; biliverdin; cancer; cytoprotective enzyme; p53; proapoptotic transcription factor p53

Document Type: Research Article

Publication date: 01 December 2012

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  • Protein & Peptide Letters publishes short papers in all important aspects of protein and peptide research, including structural studies, recombinant expression, function, synthesis, enzymology, immunology, molecular modeling, drug design etc. Manuscripts must have a significant element of novelty, timeliness and urgency that merit rapid publication. Reports of crystallisation, and preliminary structure determinations of biologically important proteins are acceptable. Purely theoretical papers are also acceptable provided they provide new insight into the principles of protein/peptide structure and function.
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