Albrecht T, Fons M P, Deng C Z, Boldogh I
Department of Microbiology and Immunology, University of Texas Medical Branch at Galveston 77555-1019, USA.
Virology. 1997 Mar 31;230(1):48-61. doi: 10.1006/viro.1997.8467.
The effect of human cytomegalovirus (HCMV) infection on the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus was studied in Chinese hamster lung V79 cells. When V79 cells were infected with HCMV (strain AD169) at multiplicities of 0.1 to 50 plaque forming units (PFU) per cell the presumptive mutation frequency, as determined by the number of 6-thioguanine-resistant (TGr) colonies, was increased up to 16.8-fold (P < 0.005), depending on the multiplicity of infection. Increases in the mutation frequency at the hprt locus were also observed for other laboratory-adapted HCMV strains (C-87, Davis) and for low passage clinical isolates (82-1, 84-2). The expression time required for the maximum increase in TGr colonies was 3 days and was consistent among the HCMV strains evaluated in this study. UV-irradiation of HCMV stock up to a dose of 9.6 x 10(4) ergs/mm2 increased the mutation frequency, but further exposure to UV light or to heat (56 degrees for 30 min) significantly decreased the frequency of TGr-resistant colonies, suggesting that expression of HCMV genes was involved in the mutation process. HCMV-induced TGr cells demonstrated substantially reduced (> 96%) incorporation of [3H]hypoxanthine. PCR analysis of the hprt locus demonstrated deletions in 9 of 19 HCMV-induced TGr colonies randomly selected for further study, while 2 of 17 spontaneously developed TGr colonies demonstrated deletions. Although insertions were not detected in spontaneously developed clones, 3 of 19 HCMV-induced TGr clones had insertions in the hprt gene. Neither HCMV-specific DNA sequences nor HCMV-specific proteins were detected in the TGr clones obtained after HCMV infection. Infection of V79 cells with HCMV also increased their sensitivity to mutation with N-methyl-N'-nitro-N-nitrosoguanidine, giving a synergistic enhancement of the mutation frequency. These results indicate that HCMV infection has the capacity to induce mutations in the cellular genome and increase the sensitivity of infected cells to mutation by genotoxic chemicals. Although inactivated HCMV particles are responsible for a modest increase in the mutation frequency, expression of HCMV genes is associated with a substantial enhancement of the mutation frequency.
在中国仓鼠肺V79细胞中研究了人巨细胞病毒（HCMV）感染对次黄嘌呤 - 鸟嘌呤磷酸核糖转移酶（hprt）基因座突变频率的影响。当V79细胞以每细胞0.1至50个空斑形成单位（PFU）的复数感染HCMV（AD169株）时，根据6 - 硫鸟嘌呤抗性（TGr）集落数确定的推定突变频率增加了16.8倍（P <0.005），这取决于感染复数。对于其他实验室适应的HCMV株（C - 87、Davis）和低传代临床分离株（82 - 1、84 - 2），也观察到hprt基因座突变频率增加。TGr集落最大增加所需的表达时间为3天，并且在本研究评估的HCMV株中是一致的。将HCMV毒株紫外线照射至9.6×10(4)尔格/mm2的剂量会增加突变频率，但进一步暴露于紫外线或加热（56℃30分钟）会显著降低TGr抗性集落的频率，这表明HCMV基因的表达参与了突变过程。HCMV诱导的TGr细胞显示[3H]次黄嘌呤的掺入量大幅降低（> 96%）。对hprt基因座的PCR分析表明，在随机选择用于进一步研究的19个HCMV诱导的TGr集落中有9个存在缺失，而17个自发产生的TGr集落中有2个存在缺失。虽然在自发产生的克隆中未检测到插入，但19个HCMV诱导的TGr克隆中有3个在hprt基因中有插入。在HCMV感染后获得的TGr克隆中未检测到HCMV特异性DNA序列或HCMV特异性蛋白质。用HCMV感染V79细胞也增加了它们对N - 甲基 - N'-硝基 - N - 亚硝基胍诱变的敏感性，使突变频率产生协同增强。这些结果表明，HCMV感染有能力诱导细胞基因组中的突变，并增加感染细胞对基因毒性化学物质诱变的敏感性。虽然灭活的HCMV颗粒导致突变频率适度增加，但HCMV基因的表达与突变频率的显著增强相关。
