mafA, a novel member of the maf proto-oncogene family, displays developmental regulation and mitogenic capacity in avian neuroretina cells

Benkhelifa, Sofia; Provot, Sylvain; Lecoq, Odile; Pouponnot, Célio; Calothy, Georges; Felder-Schmittbuhl, Marie-Paule

doi:10.1038/sj.onc.1201898

Cited by 72 publications

(65 citation statements)

References 22 publications

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“…3). Chicken L-Maf is expressed in the developing lens cells of the chicken embryo, whereas quail MafA, which is almost the same in structure to L-Maf except for one amino acid difference, is expressed in retinal cells [3]. We also detected MafA mRNA in the lens and retina of the mouse embryo (our unpublished observation).…”

Section: Discussionmentioning

confidence: 62%

“…Maf family proteins are divided into two subgroups, the large Maf and the small Maf proteins. The large Maf proteins, MafA/L-Maf/ SMaf1 [3][4][5], MafB [6], c-Maf [7], and Nrl [8], contain an acidic domain in their N-termini that acts as a transcriptional activation site. By contrast, the small Maf proteins, MafK, MafF [9], and MafG [10], lack such an acidic domain.…”

mentioning

confidence: 99%

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Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter

Kajihara

Sone

Amemiya

et al. 2003

Biochemical and Biophysical Research Communications

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Large Maf transcription factors, which are members of the basic leucine zipper (b-Zip) superfamily, have been reported to be involved in embryonic development and cell differentiation. Previously, we isolated a novel zebrafish large Maf cDNA, somite Maf1 (SMaf1), which possesses transactivational activity within its N-terminus domain. To elucidate SMaf1 function in mammals, we tried to isolate the mouse homologue of zebrafish SMaf1. We isolated the mouse homologue of zebrafish SMaf1, which is the same molecule as the recently reported MafA. MafA mRNA was detected in formed somites, head neural tube, and liver cells in the embryos. In the adult mouse, MafA transcript was amplified in the brain, lung, spleen, and kidney by RT-PCR. MafA mRNA was also detectable in b-cell line. Next, we analyzed the transcriptional activity of MafA using rat insulin promoters I and II (RIPI and II), since a part of RIP sequence was similar to the Maf recognition element (MARE) and MafA was expressed in pancreatic b-cells. MafA was able to activate transcription from RIPII, but not RIPI, in a dose dependent manner and the activity was dependent on RIPE3b/C1 sequences. In addition, the amount of MafA protein was regulated by glucose concentration. These results indicate that MafA is the homologue of zebrafish SMaf1 and acts as a transcriptional activator of the insulin gene promoter through the RIPE3b element.

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Section: Discussionmentioning

confidence: 62%

mentioning

confidence: 99%

Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter

Kajihara

Sone

Amemiya

et al. 2003

Biochemical and Biophysical Research Communications

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“…The`large' Maf proteins include c-Maf, MafA and MafB; the`small' Maf family members which lack the N terminal activation domain include MafF, MafK and MafG (Motohashi et al, 1997). cMaf (identical to retroviral v-Maf; Nishizawa et al, 1989) and MafA (Benkhelifa et al, 1998) can form stable heterodimers with Jun and can bind as Jun : Maf heterodimers to the composite DNA motif TGC TGA C TCA GCA, which also contains an internal Jun : Fos site (Kerpola and Curran, 1996). Upon retroviral overexpression, c-Maf and MafA can induce an oncogenically transformed phenotype in CEF cells (Kataoka et al, 1993;Benkhelifa et al, 1998).…”

Section: Putative Roles Of Maf Family Members Interacting With Jun Inmentioning

confidence: 99%

Distinct roles of Jun : Fos and Jun : ATF dimers in oncogenesis

2001

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“…The additional four large Maf members are c-Maf, MafB, neural retina leucine zipper, and MafA (L-Maf), which have a well conserved N-terminal transactivation domain. The MafA gene was originally isolated from avian neuroretina cells (19) and recently identified in pancreatic islets (10,11,20,21). Within the islet, MafA is localized to the beta cell, whereas expression of MafB (12) and c-Maf (21) is limited to the alpha cell.…”

Section: Western and Northern Analyses Formentioning

confidence: 99%

Oxidative Stress-mediated, Post-translational Loss of MafA Protein as a Contributing Mechanism to Loss of Insulin Gene Expression in Glucotoxic Beta Cells

Harmon

Stein

Robertson

2005

Journal of Biological Chemistry

213

166

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After the onset of type 2 diabetes, chronic hyperglycemia causes glucotoxic changes in many tissues (1, 2). Glucose toxicity in the pancreatic islet beta cell secondarily leads to further defects in beta cell function, including decreases in insulin reporter activity, gene expression, content, and secretion (3). Antioxidants have been shown to prevent these adverse changes in experimental models (4, 5). We previously observed that loss of insulin gene expression is accompanied by decreased binding to the promoter region of two important transcription factors, PDX-1 1 (STF-1, IDX-1, IPF-1) and RIPE-3b1 activator (6 -8). PDX-1 is required for pancreatic development and is a key regulator of insulin gene expression. Mutations within the RIPE-3b1/C1 element of the insulin promoter markedly reduce glucose-responsive insulin gene expression (7). We also reported that loss of RIPE-3b1 binding precedes the loss of PDX-1 binding to the insulin promoter as glucotoxicity develops (8). The chronology of these losses is likely to be important in light of a recent report that RIPE-3b1/MafA directly activates PDX-1 transcription (9).The work in this study features the use of HIT-T15 cells, a glucose-responsive beta cell line that has proven over the past decade to reproduce the molecular changes in gene expression that are caused by glucose toxicity in vivo in animal models. Since isolated islets cannot be chronically cultured to study the adverse effects of high glucose concentrations over many months, this cell line is a valuable surrogate. In our previous work, reconstitution of late passage glucotoxic HIT-T15 cells by transient transfection with PDX-1 partially restored insulin promoter activity (8). Since RIPE-3b1 had not yet been cloned, we were unable to extend our studies with this transcription factor but hypothesized that reconstitution of the cells with both PDX-1 and RIPE-3b1 activator would lead to greater recovery of insulin promoter activity. With the recent cloning and identification of RIPE-3b1 activator as MafA (10 -12), we have been able to perform new studies to examine 1) whether levels of MafA mRNA and protein are decreased in glucotoxic beta cells; 2) the mechanism of MafA protein degradation; 3) whether the antioxidant, N-acetylcysteine, can prevent glucotoxicity-induced loss of MafA protein and binding to the insulin promoter; and 4) whether overexpression of MafA and PDX-1 together can restore insulin promoter activity and mRNA levels more fully than PDX-1 alone. MATERIALS AND METHODSCell Culture-HIT-T15 cells were maintained in RPMI 1640 media containing 10% fetal bovine serum and 11.1 mM glucose as described previously (13). Cells were categorized as early passage (p71-75) or late passage (p123-128), with each passage occurring weekly. Chronic culturing of HIT-T15 cells with N-acetyl-L-cysteine (Sigma; 0.5, 1, or 5 mM) added to the media was begun at p70.

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mafA, a novel member of the maf proto-oncogene family, displays developmental regulation and mitogenic capacity in avian neuroretina cells

Cited by 72 publications

References 22 publications

Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter

Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter

Distinct roles of Jun : Fos and Jun : ATF dimers in oncogenesis

Oxidative Stress-mediated, Post-translational Loss of MafA Protein as a Contributing Mechanism to Loss of Insulin Gene Expression in Glucotoxic Beta Cells

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