Regulation of c-maf gene expression by Pax6 in cultured cells.
c-Maf is a bZip transcription factor expressed in developmental and cellular differentiation processes. Recently, a c-maf knockout mouse model, showing abnormal lens development, has been reported. In order to study the regulation mechanisms of c-maf gene expression during the differentiation process we have cloned and functionally characterized the rat c-maf (maf-2) gene. The rat c-maf gene is an intronless gene, covering a length of 3.5 kb. Transient transfection analysis of the 5'-flanking region of the c-maf gene using luciferase as the reporter gene shows that Pax6, a master transcription factor for lens development, strongly activates the c-maf promoter construct. Endogenous c-maf is also activated by the Pax6 expression vector. Electrophoresis mobility shift assay and DNase I footprinting analysis show that at least three Pax6-binding sites are located in the 5'-flanking and 5'-non-coding regions of the rat c-maf gene. The c-maf gene was also markedly activated by its own product, c-Maf, through the MARE (Maf recognition element), suggesting that a positive autoregulatory mechanism controls this gene. In situ hybridization histochemical detection of Pax6 and c-Maf in the E14 lens showed that both mRNAs are expressed in the lens equator where lens epithelial cells are differentiating to lens fiber cells. These results suggest that a Pax6/c-Maf transcription factor cascade is working in lens development.
Department of Biochemistry and Department of Ophthalmology, Hokkaido University School of Medicine, N15, W7, Kita-ku, Sapporo 060-8638, Japan. m_sakai@med.hokudai.ac.jp
M
M
Sakai
M S
MS
Serria
H
H
Ikeda
K
K
Yoshida
J
J
Imaki
S
S
Nishi
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005136:Eye Proteins; D005786:Gene Expression Regulation; D005796:Genes / Q000235:genetics; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D051257:Proto-Oncogene Proteins c-maf; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D012097:Repressor Proteins; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D005136:Eye Proteins; D018398:Homeodomain Proteins; C495609:Maf protein, rat; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; C000605733:Pax6 protein, rat; D011518:Proto-Oncogene Proteins; D051257:Proto-Oncogene Proteins c-maf; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D004247:DNA; D008156:Luciferases