Hardwicke M A, Sandri-Goldin R M
Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine 92717-4025.
J Virol. 1994 Aug;68(8):4797-810. doi: 10.1128/JVI.68.8.4797-4810.1994.
We have previously shown that the herpes simplex virus immediate-early regulatory protein ICP27 acts posttranscriptionally to affect mRNA processing (R. M. Sandri-Goldin and G. E. Mendoza, Genes Dev. 6:848-863, 1992). Specifically, in the presence of ICP27, spliced target mRNAs were decreased 5- to 10-fold in transfections with target genes containing a 5' or 3' intron. Here, we have investigated the effect of ICP27 during herpes simplex virus type 1 (HSV-1) infection on accumulation of spliced cellular mRNAs. ICP27 viral mutants have been shown to be defective in host shutoff (W. R. Sacks, C. C. Greene, D. P. Aschman, and P. A. Schaffer, J. Virol. 55:796-805, 1985). Therefore, we examined whether ICP27 could contribute to this complex process by decreasing cellular mRNA levels through its effects on host cell splicing. It was found that in infections with viral mutants defective in ICP27, the accumulated levels of three spliced host mRNAs were higher than those seen with wild-type HSV-1. The differences occurred posttranscriptionally as shown by nuclear runoff transcription assays. The stabilities of the spliced products during infection with wild-type or ICP27 mutant viruses were similar, and unspliced precursor mRNA for a viral spliced gene was detected in infections with wild-type HSV-1 but not in infections in which ICP27 was not expressed. These results suggest that the reduction in cellular mRNA levels and the accumulation of pre-mRNA are related and may be caused by an impairment in host cell splicing. These data further show that ICP27 is required for these effects to occur.
我们之前已经表明，单纯疱疹病毒立即早期调节蛋白ICP27在转录后发挥作用，影响mRNA加工（R.M.桑德里 - 戈尔丁和G.E.门多萨，《基因与发育》6:848 - 863，1992年）。具体而言，在存在ICP27的情况下，用含有5'或3'内含子的靶基因转染时，剪接后的靶mRNA减少了5至10倍。在此，我们研究了单纯疱疹病毒1型（HSV - 1）感染期间ICP27对剪接后的细胞mRNA积累的影响。已证明ICP27病毒突变体在宿主关闭方面存在缺陷（W.R.萨克斯、C.C.格林、D.P.阿施曼和P.A.谢弗，《病毒学杂志》55:796 - 805，1985年）。因此，我们研究了ICP27是否可能通过影响宿主细胞剪接来降低细胞mRNA水平，从而促成这一复杂过程。结果发现，在用ICP27缺陷的病毒突变体感染时，三种剪接后的宿主mRNA的积累水平高于野生型HSV - 1感染时的水平。如核转录分析所示，差异发生在转录后。野生型或ICP27突变病毒感染期间剪接产物的稳定性相似，在野生型HSV - 1感染中检测到病毒剪接基因的未剪接前体mRNA，但在未表达ICP27的感染中未检测到。这些结果表明，细胞mRNA水平的降低和前体mRNA的积累是相关的，可能是由宿主细胞剪接受损引起的。这些数据进一步表明，这些效应的发生需要ICP27。
