pateamine-a and Osteosarcoma

Angiogenin (ANG) is a secreted ribonuclease that cleaves tRNA to initiate a stress-response program in mammalian cells. Here we show that ANG inhibits protein synthesis and promotes arsenite- and pateamine A-induced assembly of stress granules (SGs). These effects are abrogated in cells transfected with the ANG inhibitor RNH1. Transfection of natural or synthetic 5'- but not 3'-tRNA fragments (tRNA-derived stress-induced RNAs; tiRNAs) induces the phospho-eukaryotic translation initiation factor 2alpha-independent assembly of SGs. Natural 5'-tiRNAs but not 3'-tiRNAs are capped with a 5'-monophosphate that is required for optimal SG assembly. These findings reveal that SG assembly is a component of the ANG- and tiRNA-induced stress response program.

Topics: Arsenites; Blotting, Western; Bone Neoplasms; Carrier Proteins; Cells, Cultured; Cytoplasmic Granules; Enzyme Inhibitors; Epoxy Compounds; Eukaryotic Initiation Factor-2; Fluorescent Antibody Technique; Humans; Macrolides; Osteosarcoma; Oxidative Stress; Phosphorylation; Protein Biosynthesis; Reverse Transcriptase Polymerase Chain Reaction; Ribonuclease, Pancreatic; RNA, Messenger; RNA, Small Interfering; RNA, Transfer; Teratogens; Thiazoles; Tumor Cells, Cultured

Stress granules are aggregates of small ribosomal subunits, mRNA, and numerous associated RNA-binding proteins that include several translation initiation factors. Stress granule assembly occurs in the cytoplasm of higher eukaryotic cells under a wide variety of stress conditions, including heat shock, UV irradiation, hypoxia, and exposure to arsenite. Thus far, a unifying principle of eukaryotic initiation factor 2alpha phosphorylation prior to stress granule formation has been observed from the majority of experimental evidence. Pateamine A, a natural product isolated from marine sponge, was recently reported to inhibit eukaryotic translation initiation and induce the formation of stress granules. In this report, the protein composition and fundamental progression of stress granule formation and disassembly induced by pateamine A was found to be similar to that for arsenite. However, pateamine A-induced stress granules were more stable and less prone to disassembly than those formed in the presence of arsenite. Most significantly, pateamine A induced stress granules independent of eukaryotic initiation factor 2alpha phosphorylation, suggesting an alternative mechanism of formation from that previously described for other cellular stresses. Taking into account the known inhibitory effect of pateamine A on eukaryotic translation initiation, a model is proposed to account for the induction of stress granules by pateamine A as well as other stress conditions through perturbation of any steps prior to the rejoining of the 60S ribosomal subunit during the entire translation initiation process.

Topics: Animals; Arsenites; Biological Products; Biomarkers; Cell Line, Tumor; Cytoplasmic Granules; Dose-Response Relationship, Drug; Epoxy Compounds; Eukaryotic Initiation Factor-2; Fibroblasts; Fluorescent Antibody Technique, Direct; HeLa Cells; Humans; Macrolides; Mice; Osteosarcoma; Oxidative Stress; RNA, Messenger; Thiazoles; Time Factors