Malathi Krishnamurthy, Paranjape Jayashree M, Bulanova Elena, Shim Minsub, Guenther-Johnson Jeanna M, Faber Pieter W, Eling Thomas E, Williams Bryan R G, Silverman Robert H
Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Proc Natl Acad Sci U S A. 2005 Oct 11;102(41):14533-8. doi: 10.1073/pnas.0507551102. Epub 2005 Oct 3.
Virus replication in higher vertebrates is restrained by IFNs that cause cells to transcribe genes encoding antiviral proteins, such as 2'-5' oligoadenylate synthetases. 2'-5' oligoadenylate synthetase is stimulated by dsRNA to produce 5'-phosphorylated, 2'-5'-linked oligoadenylates (2-5A), whose function is to activate RNase L. Although RNase L is required for a complete IFN antiviral response and mutations in the RNase L gene (RNASEL or HPC1) increase prostate cancer rates, it is unknown how 2-5A affects these biological endpoints through its receptor, RNase L. Presently, we show that 2-5A activation of RNase L produces a remarkable stimulation of transcription (>/=20-fold) for genes that suppress virus replication and prostate cancer. Unexpectedly, exposure of DU145 prostate cancer cells to physiologic levels of 2-5A (0.1 muM) induced approximately twice as many RNA species as it down-regulated. Among the 2-5A-induced genes are several IFN-stimulated genes, including IFN-inducible transcript 1/P56, IFN-inducible transcript 2/P54, IL-8, and IFN-stimulated gene 15. 2-5A also potently elevated RNA for macrophage inhibitory cytokine-1/nonsteroidal antiinflammatory drug-activated gene-1, a TGF-beta superfamily member implicated as an apoptotic suppressor of prostate cancer. Transcriptional signaling to the macrophage inhibitory cytokine-1/nonsteroidal antiinflammatory drug-activated gene-1 promoter by 2-5A was deficient in HeLa cells expressing a nuclease-dead mutant of RNase L and was dependent on the mitogen-activated protein kinases c-Jun N-terminal kinase and extracellular signal-regulated kinase, both of which were activated in response to 2-5A treatments. Because 2-5A and RNase L participate in defenses against viral infections and prostate cancer, our findings have implications for basic cellular mechanisms that control major pathogenic processes.
在高等脊椎动物中，病毒复制受到干扰素的抑制，干扰素可促使细胞转录编码抗病毒蛋白的基因，如2'-5'寡腺苷酸合成酶。双链RNA可刺激2'-5'寡腺苷酸合成酶产生5'-磷酸化、2'-5'-连接的寡腺苷酸（2-5A），其功能是激活RNase L。尽管RNase L是完整的干扰素抗病毒反应所必需的，且RNase L基因（RNASEL或HPC1）的突变会增加前列腺癌的发病率，但尚不清楚2-5A如何通过其受体RNase L影响这些生物学终点。目前，我们发现2-5A激活RNase L会显著刺激抑制病毒复制和前列腺癌的基因转录（≥20倍）。出乎意料的是，将DU145前列腺癌细胞暴露于生理水平的2-5A（0.1μM）时，诱导产生的RNA种类大约是其下调的两倍。在2-5A诱导的基因中，有几个是干扰素刺激基因，包括干扰素诱导转录本1/P56、干扰素诱导转录本2/P54、白细胞介素-8和干扰素刺激基因15。2-5A还能显著提高巨噬细胞抑制细胞因子-1/非甾体抗炎药激活基因-1的RNA水平，该基因是转化生长因子-β超家族成员，被认为是前列腺癌的凋亡抑制因子。在表达RNase L核酸酶失活突变体的HeLa细胞中，2-5A对巨噬细胞抑制细胞因子-1/非甾体抗炎药激活基因-1启动子的转录信号传导存在缺陷，且依赖于丝裂原活化蛋白激酶c-Jun氨基末端激酶和细胞外信号调节激酶，这两种激酶在2-5A处理后均被激活。由于2-5A和RNase L参与了针对病毒感染和前列腺癌的防御，我们的发现对控制主要致病过程的基本细胞机制具有启示意义。
