Dynamics of the metal-dependent transcription factor complex in vivo at the mouse metallothionein-I promoter.
The in vivo association of transcription factors with the metallothionein-I promoter was examined using chromatin immunoprecipitation (ChIP) assays. The results demonstrated that c-fos is rapidly recruited along with the metal response element-binding transcription factor-1 (MTF-1) to this promoter in response to zinc or cadmium, and that this recruitment is reversed in the visceral yolk sac by a zinc-deficient diet in vivo, and in cultured cells after lowering the zinc concentration in the medium or during prolonged zinc exposure. In contrast, the interactions of c-jun, USF-1, USF-2 and Sp1 with this promoter are metal-independent. Studies of knockout cells revealed that the recruitment of c-fos to the MT-I promoter requires MTF-1, but that c-fos is not essential for recruitment of MTF-1 and metal-induction of MT-I gene expression. Studies of Hepa cells stably-transfected with reporter genes driven by the MT-I promoter suggested two in vivo binding sites for USF-1 and -2. In contrast, Sp1 was apparently associated with a single binding site (upstream of -153 bp). In addition, maximal recruitment of c-fos by metals required sequences and/or other proteins that interact upstream of -153 bp. In summary, these studies extend our understanding of the complexity and dynamics of the transcription factor complex that forms at the MT-I promoter in vivo in response to metals.
Daniels
Patrick J
PJ
Department of Biochemistry and Molecular Biology, Mail Stop 3030, University of Kansas Medical Center, 39th and Rainbow Blvd., Kansas City, KS 66160-7421, USA.
Andrews
Glen K
GK
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts; D046911:Macromolecular Substances; D008668:Metallothionein / Q000235:genetics*; D008670:Metals / Q000494:pharmacology*; D051379:Mice; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D051720:Upstream Stimulatory Factors; D015032:Zinc / Q000494:pharmacology; D000097809:Transcription Factor MTF-1
D002104:Cadmium; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D008668:Metallothionein; D008670:Metals; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; D015032:Zinc; D000097809:Transcription Factor MTF-1; C497183:Usf1 protein, mouse; C497186:Usf2 protein, mouse