Gene- and cell-type-specific effects of signal transduction cascades on metal-regulated gene transcription appear to be independent of changes in the phosphorylation of metal-response-element-binding transcription factor-1

Biochem J. 2004 Aug 15;382(Pt 1):33-41. doi: 10.1042/BJ20040504.

Abstract

Post-translational modification of MTF-1 (metal-response-element-binding transcription factor-1) was suggested to play a role in its metalloregulatory functions. In the present study, pulse labelling and two-dimensional electrophoresis-Western blotting were used to demonstrate that, although MTF-1 is highly modified in vivo, its phosphorylation level does not rapidly change in response to metals, nor does its overall modification pattern. Recombinant MTF-1 was found to serve as an in vitro substrate for casein kinase II, c-Jun N-terminal kinase and protein kinase C, but inhibition of these kinases in vivo did not significantly change the modification pattern of MTF-1. Northern blotting revealed that inhibitors of casein kinase II and c-Jun N-terminal kinase severely attenuate the metal-induced transcription of the native chromatin-packaged metallothionein-I and zinc transporter-1 genes, whereas protein kinase C inhibitors exerted gene- and cell-type-specific effects on the metal regulation and basal expression of these two genes. A chromatin immunoprecipitation assay was used to demonstrate that none of these inhibitors prevent the metal-dependent recruitment of MTF-1 to the MT-I promoter. In brief, results of the present study suggest that protein kinases may not alter the phosphorylation state of MTF-1 during the rapid-response phase to metals, nor do they regulate the metal-dependent formation of a stable MTF-1-chromatin complex. Instead, protein kinases may exert their interdependent effects on metal-induced gene expression by acting on cofactors that interact with MTF-1.

MeSH terms

  • Animals
  • Cadmium / metabolism
  • Cadmium / physiology*
  • Carcinoma, Hepatocellular / enzymology
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / pathology
  • Casein Kinase II / antagonists & inhibitors
  • Casein Kinase II / metabolism
  • Cation Transport Proteins / biosynthesis
  • Cation Transport Proteins / genetics
  • Cell Line
  • Cell Line, Tumor
  • DNA-Binding Proteins
  • Enzyme Inhibitors / pharmacology
  • Fibroblasts / chemistry
  • Fibroblasts / cytology
  • Fibroblasts / metabolism
  • Gene Expression Regulation / drug effects
  • JNK Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Liver Neoplasms / enzymology
  • Liver Neoplasms / genetics
  • Liver Neoplasms / pathology
  • Mice
  • Phosphates / metabolism
  • Phosphorylation
  • Promoter Regions, Genetic / genetics
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism
  • Signal Transduction / genetics*
  • Species Specificity
  • Substrate Specificity
  • Transcription Factors / biosynthesis
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcription, Genetic / genetics*
  • Zinc / pharmacology
  • Zinc / physiology*

Substances

  • Cation Transport Proteins
  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Phosphates
  • Slc30a1 protein, mouse
  • Transcription Factors
  • transcription factor MTF-1
  • Cadmium
  • Casein Kinase II
  • Protein Kinase C
  • JNK Mitogen-Activated Protein Kinases
  • Zinc