Structural organization of the human microphthalmia-associated transcription factor gene containing four alternative promoters.
Microphthalmia-associated transcription factor (MITF) affects the development of many types of cells, including melanocytes and retinal pigment epithelium (RPE). MITF consists of at least three isoforms, MITF-A, MITF-H and MITF-M, differing at their amino-termini and expression patterns. Here, we characterize the structural organization of the human MITF gene. The gene contains at least four isoform-specific first exons, exons 1A, 1H, 1B and 1M in the 5' to 3' direction, each of which encodes the unique amino-terminus of a given isoform, including newly identified MITF-B. The 5'-flanking regions of these isoform-specific exons are termed promoters A, H, B and M, respectively, which showed different promoter activities, as judged by transient transfection assay. Promoter A directs the expression of a reporter gene in RPE, cervical cancer and melanoma cells, whereas promoter M is functional only in melanoma cells. Promoter H showed the significant activity in RPE and cervical cancer cells but not in melanoma cells. In contrast, the 1.7 kb 5'-flanking region of exon 1B showed no noticeable promoter activity in these cell lines. Therefore, alternative promoters provide the MITF gene with the diversity in transcriptional regulation and the capability of generating structurally different protein isoforms.
Udono
T
T
Department of Molecular Biology, Tohoku University School of Medicine, Aoba-ku, Sendai, Miyagi, Japan.
Yasumoto
K
K
Takeda
K
K
Amae
S
S
Watanabe
K
K
Saito
H
H
Fuse
N
N
Tachibana
M
M
Takahashi
K
K
Tamai
M
M
Shibahara
S
S
D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004847:Epithelial Cells; D005091:Exons; D005786:Gene Expression Regulation; D006801:Humans; D008850:Microphthalmos / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics; D012168:Retinal Pigments / Q000235:genetics; D015719:Single-Strand Specific DNA and RNA Endonucleases; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D014849:Waardenburg Syndrome / Q000235:genetics
D018076:DNA, Complementary; D020033:Protein Isoforms; D012168:Retinal Pigments; D014157:Transcription Factors; D015719:Single-Strand Specific DNA and RNA Endonucleases