Ihara S, Feldman L, Watanabe S, Ben-Porat T
Virology. 1983 Dec;131(2):437-54. doi: 10.1016/0042-6822(83)90510-x.
The immediate-early transcripts of pseudorabies virus have been located in a region of the genome situated internally within the inverted repeat between map positions 0.99 and 0.95. A single immediate-early transcript (approximately 6 kb) can be detected both in the cytoplasmic and nuclear fractions of infected, cycloheximide-treated cells. Analysis of the proteins synthesized after removal of cycloheximide from infected cells or after translation in vitro of the RNA isolated from these cells revealed the presence of a single protein (180K) not present in similarly treated, uninfected cells. That this is a virus protein and is specified by the immediate-early region of the genome was shown by selection and translation of mRNA hybridizing with virus DNA from the appropriate region of the genome. The effects of infection of cells with a temperature-sensitive mutant (tsG1) defective in the 180K protein were studied. At the nonpermissive temperature only immediate-early RNA was transcribed and only one virus protein, the 180K protein was synthesized. Inhibition of cellular protein and DNA synthesis was also observed. After shift down of tsG1-infected cells from the nonpermissive to the permissive temperature at 3 hr post infection, a transition to early RNA transcription occurred. However, if the shift down was delayed until 5 hr post infection, transcription of the virus genome was completely inhibited and an abortive infection ensued. Shift of the mutant-infected cells from the permissive to the nonpermissive temperature resulted in a decrease in the rate of accumulation of early and late transcripts, and a resumption of the synthesis of immediate-early RNA and protein. From these as well as from previous results, it is concluded that pseudorabies virus codes for a single multifunctional immediate-early protein which is essential for the transcription of immediate-early to early RNA and is required for the continuous transcription of early (and late) RNA. The immediate-early protein is also self-regulatory; the presence of the functional immediate-early protein represses the transcription of its RNA. In addition, the immediate-early protein of pseudorabies virus appears to play a direct role, under certain conditions, in the inhibition of cellular macromolecular synthesis.
伪狂犬病病毒的即刻早期转录物定位于基因组中位于图谱位置0.99和0.95之间反向重复序列内部的一个区域。在感染了环己酰亚胺处理的细胞的细胞质和细胞核组分中都能检测到单一的即刻早期转录物（约6 kb）。对从感染细胞中去除环己酰亚胺后或对从这些细胞中分离的RNA进行体外翻译后合成的蛋白质进行分析，发现存在一种在同样处理的未感染细胞中不存在的单一蛋白质（180K）。通过选择与基因组适当区域的病毒DNA杂交的mRNA并进行翻译，表明这是一种病毒蛋白，由基因组的即刻早期区域所编码。研究了用在180K蛋白上有缺陷的温度敏感突变体（tsG1）感染细胞的效果。在非允许温度下，仅转录即刻早期RNA，仅合成一种病毒蛋白，即180K蛋白。还观察到细胞蛋白质和DNA合成受到抑制。在感染后3小时将tsG1感染的细胞从非允许温度下调到允许温度后，发生了向早期RNA转录的转变。然而，如果下调延迟到感染后5小时，则病毒基因组的转录被完全抑制，继而发生流产感染。将突变体感染的细胞从允许温度转变为非允许温度导致早期和晚期转录物积累速率降低，并恢复即刻早期RNA和蛋白质的合成。从这些以及先前的结果可以得出结论，伪狂犬病病毒编码一种单一的多功能即刻早期蛋白，它对于即刻早期RNA转录为早期RNA是必不可少的，并且是早期（和晚期）RNA持续转录所必需的。即刻早期蛋白也是自我调节的；功能性即刻早期蛋白的存在会抑制其RNA的转录。此外，伪狂犬病病毒的即刻早期蛋白在某些条件下似乎在抑制细胞大分子合成中起直接作用。
