Mouse MafA, homologue of zebrafish somite Maf 1, contributes to the specific transcriptional activity through the insulin promoter.
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 beta-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 beta 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.
Kajihara
Miwako
M
Department of Internal Medicine, University of Tsukuba, 1-1-1, Tennodai, Tsukuba 305-8575, Japan.
Sone
Hirohito
H
Amemiya
Michiyo
M
Katoh
Yasutake
Y
Isogai
Masashi
M
Shimano
Hitoshi
H
Yamada
Nobuhiro
N
Takahashi
Satoru
S
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D018398:Homeodomain Proteins; D006801:Humans; D007328:Insulin / Q000235:genetics* / Q000378:metabolism*; D037181:Lectins, C-Type; D051473:Maf Transcription Factors, Large; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009928:Organ Specificity; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011971:Receptors, Immunologic; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012680:Sensitivity and Specificity; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D019170:Somites / Q000737:chemistry / Q000378:metabolism; D014018:Tissue Distribution; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000502:physiology*; D014981:Xenopus; D015027:Zebrafish
D018398:Homeodomain Proteins; D007328:Insulin; C113413:KLRG1 protein, human; D037181:Lectins, C-Type; C104954:MAF1 protein, S cerevisiae; D051473:Maf Transcription Factors, Large; C485160:Mafa protein, mouse; D011518:Proto-Oncogene Proteins; D011971:Receptors, Immunologic; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C084010:pancreatic and duodenal homeobox 1 protein