Characterization of the transcription factor MTF-1 from the Japanese pufferfish (Fugu rubripes) reveals evolutionary conservation of heavy metal stress response.
The pufferfish Fugu rubripes was recently introduced as a new model organism for genomic studies, since it contains a full set of vertebrate genes but only 13% as much DNA as a mammal. Fugu genes tend to be smaller and densely spaced due to shortening of introns and intergenic spacers. We isolated the Fugu gene for the metal-responsive transcription factor MTF-1 (MTF1), a mediator of heavy metal regulation and oxidative stress response previously characterized in mammals. In addition, most of the cDNA sequence was also determined. The 780 amino acid MTF-1 protein of Fugu is very similar to that of mouse and human, with 90% amino acid identity in the DNA binding zinc finger domain and 57% overall identity. Expression of the pufferfish cDNA in mammalian cells shows that Fugu MTF-1 has the same DNA binding specificity as its mammalian counterpart and also induces transcription in response to zinc and cadmium. The protein-coding part of the Fugu MTF-1 gene spans 6.4 kb and consists of 11 exons. Upstream region and first exon constitute a CpG island. The distance between stop codon and polyadenylation motifs is >2 kb, suggesting a very long 3' untranslated mRNA region, followed by another CpG island which may represent the promoter of the next gene downstream. Part of the MTF-1 genomic structure was also determined in the mouse, and some striking similarities were found: for example, the upstream adjacent gene in both species is INPP5P, encoding a phosphatase. The mouse MTF-1 promoter is also embedded in a CpG island, which however shares no sequence similarity to the one of Fugu. The Fugu CpG island is shorter than the one of the mouse and has no elevated [G+C] content; these and other data indicate that CpG islands of fish may represent a primordial stage of CpG island evolution.
Auf der Maur
A
A
Institut für Molekularbiologie der Universität Zürich, Switzerland.
Belser
T
T
Elgar
G
G
Georgiev
O
O
Schaffner
W
W
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002104:Cadmium / Q000378:metabolism*; D002461:Cell Line, Transformed; D017124:Conserved Sequence; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D019143:Evolution, Molecular; D005399:Fishes / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D007564:Japan; D051379:Mice; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*; D000097809:Transcription Factor MTF-1
D002104:Cadmium; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D014157:Transcription Factors; D015032:Zinc; D000097809:Transcription Factor MTF-1