The Polycomb-group protein ENX-2 interacts with ZAP-70.
Human ENX-2 is a homologue of Drosophila Enhancer of zeste, which is a member of Polycomb-group proteins regulating the expression of homeotic genes as chromatin-associated proteins. In this study, we demonstrate that ENX-2 plays an important role as a signaling molecule involved in T cell receptor-mediated signaling pathway. In immunoprecipitation experiments, ENX-2 and zeta associated protein-70 (ZAP-70) were co-precipitated from T cell lysate. When probed with an anti-phospho-tyrosine antibody, ENX-2 was found to be phosphorylated on tyrosine. On the other hand, ENX-2 was not phosphorylated on tyrosine in the mutant Jurkat cell, J.Cam1.6 lacking the activity of lymphocyte protein tyrosine kinase p56(lck). The interaction between ENX-2 and ZAP-70 was abolished in the mutant cell. Furthermore, in-vitro kinase assay using purified p56(lck) demonstrated that ENX-2 became tyrosine phosphorylated by this kinase. These findings show that the phosphorylation of ENX-2 is responsible for the interaction between ENX-2 and ZAP-70.
Ogawa
Motoyuki
M
Department of Anatomy, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. motoana@sc.itc.keio.ac.jp
Hiraoka
Yoshiki
Y
Aiso
Sadakazu
S
D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D019169:Jurkat Cells / Q000502:physiology; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000235:genetics; D046911:Macromolecular Substances; D009154:Mutation; D010766:Phosphorylation; D063146:Polycomb-Group Proteins; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000502:physiology; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism; D051746:ZAP-70 Protein-Tyrosine Kinase
D046911:Macromolecular Substances; D063146:Polycomb-Group Proteins; D011948:Receptors, Antigen, T-Cell; D012097:Repressor Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human