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.
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.
Jiang
Huimin
H
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160-7421, USA.
Fu
Kai
K
Andrews
Glen K
GK
D000818:Animals; D002104:Cadmium / Q000378:metabolism / Q000502:physiology*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D047390:Casein Kinase II / Q000037:antagonists & inhibitors / Q000378:metabolism; D027682:Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D002460:Cell Line; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008113:Liver Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051379:Mice; D010710:Phosphates / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D013045:Species Specificity; D013379:Substrate Specificity; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics*; D015032:Zinc / Q000494:pharmacology / Q000502:physiology*; D000097809:Transcription Factor MTF-1
D002104:Cadmium; D047390:Casein Kinase II; D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D048031:JNK Mitogen-Activated Protein Kinases; D010710:Phosphates; D011493:Protein Kinase C; D014157:Transcription Factors; D015032:Zinc; D000097809:Transcription Factor MTF-1; C485803:Slc30a1 protein, mouse