Holden V R, Zhao Y, Thompson Y, Caughman G B, Smith R H, O'Callaghan D J
Department of Microbiology and Immunology, Louisiana State University Medical Center, Shreveport 71130-3932, USA.
Virology. 1995 Jul 10;210(2):273-82. doi: 10.1006/viro.1995.1344.
The IR4 gene (inverted repeat gene 4) of equine herpesvirus type 1 (EHV-), the homolog of the herpes simplex virus type 1 ICP22 gene, is differentially expressed as a 1.4-kb early transcript and a 1.7-kb late transcript that encode a series of proteins that migrate between 42 to 47 kDa, localize to the nucleus of EHV-1-infected cells, and become packaged within EHV-1 virions (V. R. Holden, G. B. Caughman, Y. Zhao, R. N. Harty, and D. J. O'Callaghan, J. Virol. 68, 4329-4340, 1994). To assess the role of the IR4 protein in EHV-1 gene regulation, an IR4 expression vector was cotransfected with EHV-1 chimeric promoter-CAT reporter constructs and EHV-1 effector plasmids to determine the effects of the IR4 protein on the expression of immediate-early (IE), early, and late promoters. These studies revealed that the IR4 protein: (i) minimally trans-activates EHV-1 promoters, (ii) acts synergistically with the UL3 (ICP27) gene product to trans-activate the IE promoter, (iii) does not interfere with the trans-repression of the IE promoter by the IE protein, (iv) enhances transactivation of early promoters by the IE protein, (v) enhances the transactivation of both early and late promoters by the IE and UL3 proteins, and (vi) interacts synergistically with the IE protein to trans-activate the heterologous HSV-1 ICP4 promoter. These data suggest that the IR4 gene product plays a significant role in EHV-1 gene regulation.
1型马疱疹病毒（EHV-1）的IR4基因（反向重复基因4）是单纯疱疹病毒1型ICP22基因的同源物，以1.4 kb的早期转录本和1.7 kb的晚期转录本差异表达，这两种转录本编码一系列分子量在42至47 kDa之间的蛋白质，定位于EHV-1感染细胞的细胞核，并被包装在EHV-1病毒粒子中（V. R. 霍尔登、G. B. 考曼、Y. 赵、R. N. 哈蒂和D. J. 奥卡拉汉，《病毒学杂志》68，4329 - 4340，1994年）。为了评估IR4蛋白在EHV-1基因调控中的作用，将一个IR4表达载体与EHV-1嵌合启动子 - CAT报告基因构建体和EHV-1效应质粒共转染，以确定IR4蛋白对即刻早期（IE）、早期和晚期启动子表达的影响。这些研究表明，IR4蛋白：（i）对EHV-1启动子的反式激活作用最小；（ii）与UL3（ICP27）基因产物协同作用以反式激活IE启动子；（iii）不干扰IE蛋白对IE启动子的反式抑制；（iv）增强IE蛋白对早期启动子的反式激活；（v）增强IE和UL3蛋白对早期和晚期启动子的反式激活；（vi）与IE蛋白协同作用以反式激活异源的HSV-1 ICP4启动子。这些数据表明，IR4基因产物在EHV-1基因调控中起重要作用。
