An apoptotic pathway of 3'-Ethynylcytidine(ECyd) involving the inhibition of RNA synthesis mediated by RNase L - RNA

An apoptotic pathway of 3'-Ethynylcytidine(ECyd) involving the inhibition of RNA synthesis mediated by RNase L
2006
Tomoharu Naito1, Tatsushi Yokogawa1, Hye-Sook Kim1, Akira Matsuda2, Takuma Sasaki3, Masakazu Fukushima4, Yukio Kitade5 and Yusuke Wataya1
1 Faculty of Pharmaceutical Sciences, Okayama University, Okayama, Japan, 2 Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan, 3 Cancer Research Institute, Kanazawa University, Kanazawa, Japan, 4 Taiho Pharmaceutical Co., Ltd., Hanno, Japan, 5 Faculty of Engineering, Gifu University, Gifu, Japan
Nucleic Acids Symposium Series 2006
RNase L is an endoribonuclease that requires 2'-5' oligoadenylate to cleave single-stranded RNA. Although the antiviral effects of RNase L are well known because of its viral RNA degradation activity recently but it has been suggested that RNase L is concerned in mitochondrial-caspase dependent apoptotic signaling pathway induced by a number of anticancer agents. Moreover, it has variety of functions including translation and transcription of proteins. In this report, we found that 1-(3-C-ethynyl-?-D-ribo-pentofuranosyl) cytosine (ECyd), which inhibits RNA synthesis through competitive inhibition of RNA polymerase I induced 28S rRNA fragmentation. The cleavage pattern of rRNA induced by ECyd was similar and the cleavage sites were identical to those cleaved by RNase L. Additionaly, apoptosis induced by ECyd was elevated following the protein expression of RNase L in the tumor cells when treated with IFN-2a which was known to induce RNase L expression. To identify the role of RNase L in apoptosis induced by ECyd, we detected the decreased level of RNase L by several folds in the tumor cell lines through a small interfering RNA (siRNA).
These results indicated that RNase L might integrate apoptotic signals induced by ECyd and provide the possibility to be a novel clinical target for cancer chemotherapy.
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