Association of RNase L with a Ras GTPase-activating-like protein IQGAP1 in mediating the apoptosis of a human cancer cell-line.
Mammalian intracellular ribonuclease L (RNase L) is a latent endoribonuclease that functions against viral infections as an apoptosis-inducing protein, and its activity requires intracellular 5'-end-triphosphorylated-2',5' oligoadenylates (2-5A) as an activator. Previously, we showed that RNase L can be activated in human cancer cell line HT1080 by an RNA polymerase I inhibitor, 1-(3-C-ethynyl-β-D-ribo-pentofuranosyl)cytosine (3'-ethynylcytidine; ECyd). In ECyd-treated cells, knockdown of the RNase L resulted in a marked decrease in c-jun N-terminal kinase (JNK) phosphorylation, thereby inhibiting apoptosis. We investigate RNase L binding partners by focused proteomic approach using immunoprecipitation with anti-RNase L IgG and mass spectrometry. We found that the IQ motif-containing Ras GTPase-activating-like protein 1 (IQGAP1) can associate with RNase L, and that phosphorylation occurs on the IQGAP1. ECyd-induced JNK phosphorylation and apoptosis were inhibited when IQGAP1 was knocked down with a small interfering RNA. These results raise the interesting possibility that the RNase L-IQGAP1 association may regulate JNK phosphorylation in RNase L-madiated apoptosis. It is likely IQGAP1 works as a regulator in apoptosis.
Sato
Akira
A
Department of Molecular Drug Informatics, Faculty of Pharmaceutical Sciences, Tsushima, Okayama, Okayama University, Japan.
Naito
Tomoharu
T
Hiramoto
Akiko
A
Goda
Kazato
K
Omi
Takuya
T
Kitade
Yukio
Y
Sasaki
Takuma
T
Matsuda
Akira
A
Fukushima
Masakazu
M
Wataya
Yusuke
Y
Kim
Hye-Sook
HS
D017209:Apoptosis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival; D003562:Cytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D020287:In Situ Nick-End Labeling; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D025941:Protein Interaction Mapping / Q000379:methods; D034622:RNA Interference; D020703:ras GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*
C103084:1-(3-C-ethynylribopentofuranosyl)cytosine; C101203:IQ motif containing GTPase activating protein 1; D020703:ras GTPase-Activating Proteins; D003562:Cytidine; D048031:JNK Mitogen-Activated Protein Kinases; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease