Transcriptional regulation of the human manganese superoxide dismutase gene: the role of specificity protein 1 (Sp1) and activating protein-2 (AP-2)

Abstract

Manganese superoxide dismutase (MnSOD) plays an important role in regulating cellular redox conditions. Expression of MnSOD has been shown to protect against damage by oxidative stress and to suppress the malignant phenotype of human cancer cells. We have previously cloned the human MnSOD (SOD2) gene and analysed its 5′ proximal promoter, which has been characterized by a lack of a TATA or CAAT box and the presence of multiple GC boxes. To define further the molecular mechanisms for the regulation of MnSOD expression, multiple transcription factor-binding motifs containing overlapping specificity protein 1 (Sp1)- and activator protein (AP)-2-binding sites were identified by DNase I footprinting analysis. Functional studies in three cell lines with different levels of Sp1 and AP-2 proteins suggested that the cellular levels of these proteins may differentially regulate transcription via GC-binding motifs in the human SOD2 promoter. Co-transfection of an Sp1 expression vector resulted in an increase in the transcription of the promoter-driven reporter gene. In contrast, co-transfection of the AP-2 expression vector caused a decrease in transcription. Direct mutagenesis analysis of Sp1- and AP-2-binding sites showed that Sp1 is essential for transcription of the human SOD2 gene, whereas AP-2 plays a negative role in the transcription. Immunoprecipitation of Sp1 and AP-2 proteins demonstrated that Sp1 interacts with AP-2 in vivo. Two-hybrid analysis revealed that interaction between Sp1 and AP-2 plays both a positive and negative role in the transcription of the reporter gene in vivo. Taken together, our data indicate that AP-2 down-regulates transcription of the human SOD2 gene via its interaction with Sp1 within the promoter region. These findings, coupled with our previous observation that several cancer cell lines have mutations in the promoter region of the human MnSOD gene, which lead to an increase in an AP-2-binding site and a decrease in the promoter activity, signal the importance of understanding the promoter structure and the regulation of the human SOD2 gene by Sp1 and AP-2.

Colored Potato Extracts Induce Superoxide Dismutase-2 mRNA Via ERK1/2 Pathway in HepG2 Cells

“…For instance, superoxide dismutase (SOD)-2 or manganese SOD is a mitochondrial enzyme that exists in the matrix of mitochondria [5,6] and scavenges ROS leaked from the respiratory chain. Tumor necrosis factor-α (TNF-α) and oxidative stresses [7,8] promote the expression of SOD-2 mRNA, the transcription of which is regulated by activation of extracellular signal-related kinase (ERK)1/2 pathway and subsequent nuclear factor-kappa B (NF-κB), Sp1, and/or histone acetylation [9][10][11].…”

Selenium supplementation increases liver MnSOD expression: Molecular mechanism for hepato-protection

“…The promoter region of the MnSOD gene has several SP1 and AP-2 binding sites. SP1 activates transcription of the gene, whereas AP-2 competes with SP1 to down-regulate its transcriptional activity [23]. Indeed, reports indicate that the ratio between these two transcription factors controls genes transcription [27,28].…”

“…The promoter region of the MnSOD gene contains several SP1 and AP-2 binding sites: SP1 is essential for transcription of the MnSOD gene, whereas AP-2 has a negative effect on this gene's transcription [22,23]. To study the effect of sSe on SP1 and AP-2 DNA-binding activity, hepatocytes were isolated from rat liver and cultured.…”

A novel murrel Channa striatus mitochondrial manganese superoxide dismutase: gene silencing, SOD activity, superoxide anion production and expression

“…So far, a number of MnSOD orthologs have been characterized from mammals (Ho et al 1991;Wan et al 1994;Meyrick and Magnuson 1994;Jones et al 1995), fish (Lin et al 2009;Zhang et al 2011) and invertebrates (Gomez-Anduro et al 2006;Bao et al 2008;Lin et al 2010;Yu et al 2011). However, reports on the mechanisms of transcriptional regulation of MnSOD from fish are fewer than from mammals (Yeh et al 1998;Xu et al 2002;Clair et al 2002), and from striped murrel Channa striatus, the details are nil. Hence, it is necessary to study the characterization of mMnSOD from C. striatus at molecular level to understand its immune system.…”