The growth factor-inducible immediate-early gene 3CH134 encodes a protein-tyrosine-phosphatase.
Stimulation of fibroblasts with serum growth factors results in the rapid activation of a set of immediate-early genes, among them 3CH134. We have purified a bacterially expressed form of the 3CH134-encoded polypeptide and demonstrated that it has intrinsic protein-tyrosine-phosphatase (PTPase; protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48) activity in vitro. This activity is optimal at pH 7.5, is sensitive to vanadate and cysteinyl modifying agents, and is insensitive to a panel of serine/threonine phosphatase inhibitors. Purified 3CH134 protein displays a high degree of selectivity among the tyrosine-phosphorylated polypeptide substrates tested. Under our assay conditions, the rates of dephosphorylation are in the order EDNDYINASL peptide < myelin basic protein < reduced, carboxyamidomethylated, and maleylated lysozyme (RCML) < p42mapk. There is a 200-fold range in rates for these substrates, with p42mapk dephosphorylated 15-fold more rapidly than RCML. Although 3CH134 is most closely related to the tyrosine/serine dual-specificity phosphatase VH1, we failed to detect any 3CH134-directed activity on casein or RCML phosphorylated on serine/threonine residues by cAMP-dependent protein kinase. Since 3CH134 expression is controlled transcriptionally and posttranscriptionally, it may represent a class of PTPases whose activity is regulated at the level of protein synthesis and degradation.
Department of Genetics, University of Illinois College of Medicine, Chicago 60612-7309.
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Charles
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D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018797:Cell Cycle Proteins; D002460:Cell Line; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D054638:Dual Specificity Phosphatase 1; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D017874:Immediate-Early Proteins; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009036:Moths; D010749:Phosphoprotein Phosphatases; D011494:Protein Kinases / Q000378:metabolism; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D011506:Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D011972:Receptor, Insulin; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014158:Transcription, Genetic; D014162:Transfection
D018797:Cell Cycle Proteins; D006133:Growth Substances; D017874:Immediate-Early Proteins; D011506:Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; C517020:Dusp1 protein, mouse; D017027:Protein Tyrosine Phosphatases