Functional domains of the heavy metal-responsive transcription regulator MTF-1
Metallothioneins (MTs) constitute a class of low molecular weight, cysteine-rich, metal binding proteins which are regulated at the level of gene transcription in response to heavy metals and other adverse treatments. We have previously cloned a zinc finger factor (MTF-1) that binds specifically to heavy metal-responsive DNA sequence elements in metallothionein promoters and shown that this factor is essential for basal and heavy metal-induced transcription. Here we report that the C-terminal part of MTF-1 downstream of the DNA binding zinc fingers harbours three different transactivation domains, namely an acidic domain, a proline-rich domain and a domain rich in serine and threonine. When fused to the heterologous DNA binding domain of the yeast factor GAL4 these activation domains function constitutively, i.e. transcription of a GAL4-driven reporter gene is not induced by heavy metals. In search of the region(s) responsible for metal induction, external and internal deletion mutations of mouse and human MTF-1 and chimeric variants thereof were tested with a reporter gene driven by a metal-responsive promoter. The N-terminal part of MTF-1 containing the zinc fingers, which are dependent on zinc for efficient DNA binding, can indeed confer a limited (3- to 4-fold) zinc-responsive transcription when fused to the heterologous activation domain of the viral VP16 protein. Another region containing the acidic and proline-rich activation domains also contributes to metal inducibility, but only in the context of intact MTF-1. This indicates that the activity of MTF-1 results from a complex interplay of different functional domains.
- URL: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&dopt=Citation&list_uids=7610056
Keywords: Base Sequence ; Binding Sites ; DNA/*metabolism ; Fungal Proteins/chemistry/genetics/metabolism ; Gene Deletion ; Hela Cells ; Herpes Simplex Virus Protein Vmw65/chemistry/genetics ; Humans ; Hydrogen-Ion Concentration ; Metallothionein/*genetics ; Metals/*pharmacology ; Molecular Sequence Data ; Mutagenesis ; Plasmids ; Proline/analysis ; Promoter Regions (Genetics) ; Recombinant Fusion Proteins/chemistry/metabolism ; *Saccharomyces cerevisiae Proteins ; Serine/analysis ; Threonine/analysis ; Trans-Activation (Genetics) ; Transcription Factors/*chemistry/genetics/metabolism ; Zinc Fingers
Institut fur Molekularbiologie II der Universitat Zurich, Switzerland.
Record created on 2006-12-05, modified on 2016-08-08