Banerjee S, An S, Zhou A, Silverman R H, Makino S
Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-1019, USA.
J Virol. 2000 Oct;74(19):8793-802. doi: 10.1128/jvi.74.19.8793-8802.2000.
We characterized a novel 28S rRNA cleavage in cells infected with the murine coronavirus mouse hepatitis virus (MHV). The 28S rRNA cleavage occurred as early as 4 h postinfection (p.i.) in MHV-infected DBT cells, with the appearance of subsequent cleavage products and a decrease in the amount of intact 28S rRNA with increasing times of infection; almost all of the intact 28S rRNA disappeared by 24 h p.i. In contrast, no specific 18S rRNA cleavage was detected in infected cells. MHV-induced 28S rRNA cleavage was detected in all MHV-susceptible cell lines and all MHV strains tested. MHV replication was required for the 28S rRNA cleavage, and mature cytoplasmic 28S rRNA underwent cleavage. In certain combination of cells and viruses, pretreatment of virus-infected cells with interferon activates a cellular endoribonuclease, RNase L, that causes rRNA degradation. No interferon was detected in the inoculum used for MHV infection. Addition of anti-interferon antibody to MHV-infected cells did not inhibit 28S rRNA cleavage. Furthermore, 28S rRNA cleavage occurred in an MHV-infected mouse embryonic fibroblast cell line derived from RNase L knockout mice. Thus, MHV-induced 28S rRNA cleavage was independent of the activation of RNase L. MHV-induced 28S rRNA cleavage was also different from apoptosis-related rRNA degradation, which usually occurs concomitantly with DNA fragmentation. In MHV-infected 17Cl-1 cells, 28S rRNA cleavage preceded DNA fragmentation by at least 18 h. Blockage of apoptosis in MHV-infected 17Cl-1 cells by treatment with a caspase inhibitor did not block 28S rRNA cleavage. Furthermore, MHV-induced 28S rRNA cleavage occurred in MHV-infected DBT cells that do not show apoptotic signs, including activation of caspase-3 and DNA fragmentation. Thus, MHV-induced 28S rRNA cleavage appeared to differ from any rRNA degradation mechanism described previously.
我们对感染鼠冠状病毒小鼠肝炎病毒(MHV)的细胞中一种新的28S rRNA切割现象进行了表征。在感染MHV的DBT细胞中,28S rRNA切割最早在感染后4小时(p.i.)出现,随着感染时间的增加,随后出现切割产物,完整28S rRNA的量减少;到感染后24小时,几乎所有完整的28S rRNA都消失了。相比之下,在感染细胞中未检测到特异性的18S rRNA切割。在所有测试的MHV易感细胞系和所有MHV毒株中均检测到MHV诱导的28S rRNA切割。28S rRNA切割需要MHV复制,成熟的细胞质28S rRNA会发生切割。在某些细胞和病毒的组合中,用干扰素预处理病毒感染细胞会激活一种细胞内核糖核酸酶RNase L,导致rRNA降解。在用于MHV感染的接种物中未检测到干扰素。向MHV感染细胞中添加抗干扰素抗体并不能抑制28S rRNA切割。此外,在源自RNase L基因敲除小鼠的MHV感染的小鼠胚胎成纤维细胞系中也发生了28S rRNA切割。因此,MHV诱导的28S rRNA切割与RNase L的激活无关。MHV诱导的28S rRNA切割也不同于通常与DNA片段化同时发生的凋亡相关rRNA降解。在MHV感染的17Cl-1细胞中,28S rRNA切割比DNA片段化至少提前18小时。用半胱天冬酶抑制剂处理MHV感染的17Cl-1细胞以阻断凋亡,并不会阻断28S rRNA切割。此外,在未表现出凋亡迹象(包括半胱天冬酶-3激活和DNA片段化)的MHV感染的DBT细胞中也发生了MHV诱导的28S rRNA切割。因此,MHV诱导的28S rRNA切割似乎不同于先前描述的任何rRNA降解机制。