Isolation of the human genes encoding the pyst1 and Pyst2 phosphatases: characterisation of Pyst2 as a cytosolic dual-specificity MAP kinase phosphatase and its catalytic activation by both MAP and SAP kinases.
We have isolated the human genes encoding the Pyst1 (MKP-3) and Pyst2 (MKP-X) MAP kinase phosphatases. Both genes consist of three exons interrupted by two introns and lack an intron which is conserved in all the other members of this gene family characterised to date. This reinforces the conclusion that Pyst1 and Pyst2 are members of a distinct and structurally homologous subfamily of dual-specificity (Thr/Tyr) MAP kinase phosphatases. We find that Pyst2 mRNA is constitutively expressed in a wide variety of human cell lines including those derived from ovarian, bladder and breast cancers. While there is no evidence for inducible expression of Pyst2 mRNA in human skin fibroblasts in response to cellular stress, Pyst2 mRNA levels are moderately increased in response to serum stimulation. Pyst2 protein is predominantly cytosolic when expressed in COS-1 cells. In common with Pyst1, Pyst2 shows substrate selectivity for the classical p42 (ERK2) isoform of MAP kinase both in vitro and in vivo, displaying much reduced activity towards stress activated MAP kinase isoforms such as JNK-1 and p38/RK. Pyst2 binds p42 MAP kinase in vivo and both MAP kinase binding and substrate selectivity correlate with the ability of different recombinant MAP and SAP kinases to cause catalytic activation of the Pyst2 phosphatase in vitro.
Dowd
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ICRF Molecular Pharmacology Unit, Biomedical Research Centre, Ninewells Hospital, Dundee DD1 9SY, Scotland, UK.
Sneddon
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D000818:Animals; D019556:COS Cells; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D054642:Dual Specificity Phosphatase 6; D004789:Enzyme Activation / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology; D005455:Fluorescent Antibody Technique; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006133:Growth Substances / Q000494:pharmacology; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000502:physiology; D012867:Skin / Q000166:cytology / Q000201:enzymology; D013312:Stress, Physiological / Q000503:physiopathology; D014162:Transfection
D006133:Growth Substances; D012333:RNA, Messenger; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D020928:Mitogen-Activated Protein Kinases; C517035:DUSP6 protein, human; D054642:Dual Specificity Phosphatase 6; D017027:Protein Tyrosine Phosphatases