Zinc-induced formation of a coactivator complex containing the zinc-sensing transcription factor MTF-1, p300/CBP, and Sp1.
Herein, the mechanisms of transactivation of gene expression by mouse metal response element-binding transcription factor 1 (MTF-1) were investigated. Evidence obtained from coimmunoprecipitation assays revealed that exposure of the cells to zinc resulted in the rapid formation of a multiprotein complex containing MTF-1, the histone acetyltransferase p300/CBP, and the transcription factor Sp1. Down-regulation of endogenous p300 expression by small interfering RNA transfection significantly decreased zinc-dependent metallothionein I (MT-I) gene transcription without altering induction of zinc transporter 1 (ZnT1). MTF-1 independently facilitated the recruitment of Sp1 and p300 to the protein complex in response to zinc. Mutagenesis demonstrated that the acidic domain, one of three transactivation domains of MTF-1, is required for recruitment of p300 but not Sp1 as well as for zinc-dependent activation of MT-I gene transcription. Furthermore, mutation of leucine residues (L-->A) within a nuclear exclusion signal in the MTF-1 acidic domain impaired recruitment of p300 and zinc-dependent activation of the MT-I gene. Nuclear magnetic resonance characterization of an isolated protein fragment corresponding to the MTF-1 acidic region demonstrated that this region is largely unstructured in the presence and absence of excess stoichiometric amounts of zinc. This suggests that the mechanism by which MTF-1 recruits p300 to this complex involves extrinsic-zinc-dependent steps. These studies reveal a novel zinc-responsive mechanism requiring an acidic region of MTF-1 that functions as a nuclear exclusion signal as well as participating in formation of a coactivator complex essential for transactivation of MT-I gene expression.
Li
Yong
Y
Department of Biochemistry and Molecular Biology, Mail Stop 3030, University of Kansas Medical Center, 39th and Rainbow Blvd., Kansas City, KS 66160-7421, USA.
Kimura
Tomoki
T
Huyck
Ryan W
RW
Laity
John H
JH
Andrews
Glen K
GK
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D047468:Immunoprecipitation; D007930:Leucine; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D017384:Sequence Deletion; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D013997:Time Factors; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D015032:Zinc / Q000494:pharmacology*; D050880:p300-CBP Transcription Factors / Q000378:metabolism*; D000097809:Transcription Factor MTF-1
D002104:Cadmium; D004268:DNA-Binding Proteins; D007930:Leucine; D008668:Metallothionein; D034741:RNA, Small Interfering; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; D015032:Zinc; D050880:p300-CBP Transcription Factors; D000097809:Transcription Factor MTF-1