Keil G M, Ebeling-Keil A, Koszinowski U H
J Virol. 1987 Feb;61(2):526-33. doi: 10.1128/JVI.61.2.526-533.1987.
Cloned genomic fragments from the region (0.769 to 0.818 map units) coding for immediate-early (IE) transcripts of murine cytomegalovirus (MCMV) were used to analyze the physical organization of this region, the direction of transcription, and the proteins synthesized in vitro. Three IE transcription units could be identified. From IE coding region 1 (ie1; 0.781 to 0.796 map units) a dominant 2.75-kilobase (kb) RNA was transcribed from right to left on the prototype arrangement of the MCMV genome which directed the synthesis of an 89,000-molecular-weight polypeptide (89K polypeptide), the major IE protein. This phosphoprotein (pp89) has been shown to be active in the regulation of transcription. Upstream of ie1 and separated by the MCMV enhancer sequence was a second IE coding region, ie2, which was mapped at 0.803 to 0.817 map units. From ie2 a 1.75-kb RNA of moderate abundance was transcribed in the direction opposite to that of the ie1 RNA. After hybrid selection of the ie2 transcript, a 43,000-molecular-weight translation product was detected. A third coding region, ie3, was located directly downstream of ie1 (0.773 to 0.781 map units). The series of RNAs with low abundance, terminating in ie3, probably used the ie1 transcription start site and ranged from 1.0 to 5.1 kb in size. The 5.1-kb RNA apparently represents the nonspliced transcript from both coding regions ie1 and ie3. A 15K polypeptide was translated in vitro from RNA that was hybrid selected by ie3 sequences. Immunoprecipitation with monoclonal antibody revealed that 31K to 67K polypeptides were related to pp89. Some of these proteins were translated from RNAs that were smaller than 2.75 kb. Polypeptides related to pp89 were also synthesized in vivo. Because polypeptides unrelated to pp89 that were translated from RNA that was selected by ie2 and ie3 sequences were not immunoprecipitated by murine antisera, we assumed that the amount of these proteins synthesized in vivo during infection was probably very low.
利用来自编码鼠巨细胞病毒（MCMV）即刻早期（IE）转录本的区域（0.769至0.818个图距单位）的克隆基因组片段，分析该区域的物理组织、转录方向以及体外合成的蛋白质。可鉴定出三个IE转录单位。在MCMV基因组的原型排列上，从IE编码区1（ie1；0.781至0.796个图距单位）转录出一个占主导地位的2.75千碱基（kb）RNA，其转录方向是从右至左，该RNA指导合成一种89,000分子量的多肽（89K多肽），即主要的IE蛋白。这种磷蛋白（pp89）已被证明在转录调控中具有活性。在ie1上游且被MCMV增强子序列隔开的是第二个IE编码区ie2，其定位在0.
