Cadmium-responsive element of the human heme oxygenase-1 gene mediates heat shock factor 1-dependent transcriptional activation.
Transcription of a number of mammalian genes is activated by heavy metals, but mechanisms of signaling and transcriptional regulation are not well understood. From a comparison of heavy metal responses of several human genes, it was noted that the heme oxygenase-1 (HO-1) gene is quite similar in the spectrum of metal response and induction kinetics to the heat shock protein 70 (HSP70) gene, suggesting a common regulatory mechanism shared by these genes. The cadmium-responsive element (CdRE) known to be responsible for the metal regulation of ho-1 formed complexes with proteins from heavy metal-treated HeLa cells in an electrophoretic mobility shift assay (EMSA). These complexes were indistinguishable in mobility from those formed by the heat shock factor 1 (HSF1) and the heat shock element involved in hsp70 regulation, suggesting the involvement of HSF1 also in the CdRE complexes. Competitive EMSA and supershift analysis with an anti-HSF1 antibody revealed that HSF1 was in fact a component of the CdRE complexes. A fine analysis on the affinity of HSF1 to a series of mutant CdRE sequences showed that HSF1 recognizes a sequence motif TnCTAGA. Transient transfection analysis with overexpressed recombinant HSF1 demonstrated that CdRE has HSF1-dependent enhancer-like activity that requires direct binding of HSF1. In the absence of overexpressed HSF1, however, CdRE by itself was insufficient to mediate heavy metal-induced transcription, suggesting requirement of additional regulatory sequences. The finding that HSF1 is directly involved in the regulation of ho-1 with an anti-oxidative role revealed a new aspect of the biological defense mechanism.
Koizumi
Shinji
S
Mechanism of Health Effect Research Group, National Institute of Occupational Safety and Health, Kawasaki 214-8585, Japan. koizumi@h.jniosh.go.jp
Gong
Pengfei
P
Suzuki
Kaoru
K
Murata
Mie
M
D001483:Base Sequence; D001667:Binding, Competitive; D002104:Cadmium / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006367:HeLa Cells; D000076249:Heat Shock Transcription Factors; D051547:Heme Oxygenase-1 / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D004268:DNA-Binding Proteins; C000619706:HSF1 protein, human; D018840:HSP70 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D014157:Transcription Factors; D002104:Cadmium; D051547:Heme Oxygenase-1; D010100:Oxygen