title: A novel apoptotic pathway of 3'-Ethynylcytidine(ECyd) involving the inhibition of RNA synthesis--the possibility of RNase L activated pathway as a target of ECyd.
abstract: RNase L functions as a tumor suppressor protein due to its role in apoptosis during viral infections and various agents treatment. RNase L-mediated apoptosis is accompanied by cytochrome c release from mitochondria and requires caspase-3 activity. It was reported that RNase L is involved in JNK activation during viral infections, and that JNK is essential for apoptosis in response to RNase L activation. However, the proximal signals of RNase L that trigger JNK activation have not as yet been identified, and it is possible that the interactions between RNase L and other proteins play an important role in the RNase L-JNK apoptotic signal pathway. To investigate this hypothesis, we attempted to identify the proteins associated with RNase L using coimmunoprecipitation. In this study, we found that RNase L was associated with other proteins. Here we identified the protein X by LC-MS/MS analysis. We demonstrated that this association was increased in the presence of activated RNase L. Moreover, Protein X was phosphorylated during the activation of RNase L by treatment with cytotoxic agent, ECyd, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl) cytosine and 2-5A. To reveal the role of protein X in RNase L-mediated apoptosis, we decreased the level of protein X by a small interfering RNA (siRNA). As a result, protein X deficient cells became resistant to the apoptosis mediated by RNase L, suggesting that protein X is related to RNase L-mediated apoptosis following JNK activation. Therefore, in this study, we report the identification of a novel protein, protein X that transduces between RNase L and JNK signals.
authors.affiliation: Faculty of Pharmaceutical Sciences, Okayama University, Okayama, Japan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Naito
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Yokogawa
authors.forename: Hye-Sook
authors.initials: HS
authors.lastname: Kim
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuda
authors.forename: Takuma
authors.initials: T
authors.lastname: Sasaki
authors.forename: Masakazu
authors.initials: M
authors.lastname: Fukushima
authors.forename: Yukio
authors.initials: Y
authors.lastname: Kitade
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Wataya
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D003562:Cytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004722:Endoribonucleases / Q000378:metabolism*; D004789:Enzyme Activation; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D012313:RNA / Q000096:biosynthesis*
chemical_list: C103084:1-(3-C-ethynylribopentofuranosyl)cytosine; D000970:Antineoplastic Agents; D019384:Nucleic Acid Synthesis Inhibitors; D003562:Cytidine; D012313:RNA; D048031:JNK Mitogen-Activated Protein Kinases; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease