Members of the large Maf transcription family regulate insulin gene transcription in islet beta cells.
The C1/RIPE3b1 (-118/-107 bp) binding factor regulates pancreatic-beta-cell-specific and glucose-regulated transcription of the insulin gene. In the present study, the C1/RIPE3b1 activator from mouse beta TC-3 cell nuclear extracts was purified by DNA affinity chromatography and two-dimensional gel electrophoresis. C1/RIPE3b1 binding activity was found in the roughly 46-kDa fraction at pH 7.0 and pH 4.5, and each contained N- and C-terminal peptides to mouse MafA as determined by peptide mass mapping and tandem spectrometry. MafA was detected in the C1/RIPE3b1 binding complex by using MafA peptide-specific antisera. In addition, MafA was shown to bind within the enhancer region (-340/-91 bp) of the endogenous insulin gene in beta TC-3 cells in the chromatin immunoprecipitation assay. These results strongly suggested that MafA was the beta-cell-enriched component of the RIPE3b1 activator. However, reverse transcription-PCR analysis demonstrated that mouse islets express not only MafA but also other members of the large Maf family, specifically c-Maf and MafB. Furthermore, immunohistochemical studies revealed that at least MafA and MafB were present within the nuclei of islet beta cells and not within pancreas acinar cells. Because MafA, MafB, and c-Maf were each capable of specifically binding to and activating insulin C1 element-mediated expression, our results suggest that all of these factors play a role in islet beta-cell function.
Matsuoka
Taka-aki
TA
Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
Zhao
Li
L
Artner
Isabella
I
Jarrett
Harry W
HW
Friedman
David
D
Means
Anna
A
Stein
Roland
R
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D001665:Binding Sites; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology / Q000502:physiology*; D037181:Lectins, C-Type; D046911:Macromolecular Substances; D051473:Maf Transcription Factors, Large; D051258:MafB Transcription Factor; D013058:Mass Spectrometry; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D051257:Proto-Oncogene Proteins c-maf; D011971:Receptors, Immunologic; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D030161:Avian Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007328:Insulin; C113413:KLRG1 protein, human; D037181:Lectins, C-Type; C495607:MAF protein, human; C485159:MAFA protein, human; C490407:MAFB protein, human; D046911:Macromolecular Substances; D051473:Maf Transcription Factors, Large; C495608:Maf protein, mouse; D051258:MafB Transcription Factor; C485160:Mafa protein, mouse; C490406:Mafb protein, mouse; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D051257:Proto-Oncogene Proteins c-maf; D011971:Receptors, Immunologic; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein