title: Human T-cell leukemia virus type 1 Tax attenuates gamma-irradiation-induced apoptosis through physical interaction with Chk2.
abstract: Checkpoint kinase 2 (Chk2) is known to mediate diverse cellular responses to genotoxic stress. The fundamental role of Chk2 is to regulate the network of genome-surveillance pathways that coordinate cell-cycle progression with DNA repair and cell survival or death. Defects in Chk2 contribute to the development of both hereditary and sporadic human cancers. We now present evidence that the human T-cell leukemia virus type-1 (HTLV-1) Tax protein directly interacts with Chk2 and the kinase activity of Chk2 is inhibited by Tax. The physical interaction of Chk2 and Tax was observed by co-immunoprecipitation assays in HTLV-1-infected T cells (C81) as well as GST pull-down assays using purified proteins. Binding and kinase activity inhibition studies with Tax deletion mutants indicated that at least two domains of Tax mediate the interaction with Chk2. We have analysed the functional consequence of de novo expression of Tax upon the cellular DNA-damage-induced apoptosis, which is mediated by Chk2. Using transient transfection and TUNEL assay, we found that gamma-irradiation-induced apoptosis was decreased in 293T and HCT-116 (p53(-/-)) cells expressing HTLV-1 Tax. Our studies demonstrate an important potential target of Tax in cellular transformation.
authors.affiliation: Virus Tumor Biology Section, Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: H U
authors.initials: HU
authors.lastname: Park
authors.forename: S-J
authors.initials: SJ
authors.lastname: Jeong
authors.forename: J-H
authors.initials: JH
authors.lastname: Jeong
authors.forename: J H
authors.initials: JH
authors.lastname: Chung
authors.forename: J N
authors.initials: JN
authors.lastname: Brady
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D064447:Checkpoint Kinase 2; D017931:DNA Primers; D005720:Gamma Rays; D016356:Gene Products, tax / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
chemical_list: D017931:DNA Primers; D016356:Gene Products, tax; D016159:Tumor Suppressor Protein p53; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human; D017346:Protein Serine-Threonine Kinases