Araujo J C, Doniger J, Kashanchi F, Hermonat P L, Thompson J, Rosenthal L J
Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, D.C. 20007, USA.
J Virol. 1995 Aug;69(8):4933-40. doi: 10.1128/JVI.69.8.4933-4940.1995.
Human herpesvirus 6 strain U1102 (HHV-6A) was shown to contain a 1,473-bp functional transformation suppressor gene (ts). ts exhibited 24% identity and 51% similarity to adeno-associated virus type 2 Rep68/78. Like adeno-associated virus type 2 Rep68/78, HHV-6A ts suppressed H-ras transformation of NIH 3T3 cells. Suppression of H-ras transformation was eliminated by translation termination linker mutation at amino acid 25, 125, or 245. These data indicated the importance of the C-terminal portion of the ts protein. H-ras transformation was suppressed by ts only when H-ras was expressed by its endogenous H-ras promoter and not when it was expressed by the heterologous murine osteosarcoma virus long terminal repeat (LTR). Furthermore, ts suppressed chloramphenicol acetyltransferase (CAT) activity when the CAT gene was expressed from the H-ras promoter but not the murine osteosarcoma virus LTR promoter. Taken together, the data showed that ts suppressed H-ras transformation at the level of the H-ras promoter. To further identify the interaction of ts with transcriptional regulatory elements, the human immunodeficiency virus type 1 (HIV-1) LTR was used. This promoter was selected because it has well-defined transcriptional regulatory elements for both basal and activated transcription, because its activity is inhibited by the Rep68/78 gene, and because both HHV-6 and HIV-1 naturally infect CD4+ T cells in vivo and have been shown to infect the same cell in vitro. ts suppressed expression from both wild-type and upstream mutant HIV-1 LTR-CAT constructs. However, downstream HIV-1 TAR mutations reversed ts suppression, indicating that TAR is one of the critical elements involved. The data presented demonstrated that HHV-6A ts functionally suppressed H-ras transformation and HIV-1 LTR expression and thus that it may be useful in future gene therapy.
人疱疹病毒6型U1102株（HHV-6A）被证明含有一个1473碱基对的功能性转化抑制基因（ts）。ts与2型腺相关病毒Rep68/78有24%的同一性和51%的相似性。与2型腺相关病毒Rep68/78一样，HHV-6A ts抑制NIH 3T3细胞的H-ras转化。在氨基酸25、125或245处的翻译终止连接突变消除了对H-ras转化的抑制。这些数据表明ts蛋白C末端部分的重要性。仅当H-ras由其内源性H-ras启动子表达时，ts才抑制H-ras转化，而当它由异源鼠骨肉瘤病毒长末端重复序列（LTR）表达时则不然。此外，当氯霉素乙酰转移酶（CAT）基因由H-ras启动子表达时，ts抑制其活性，但对鼠骨肉瘤病毒LTR启动子则无此作用。综上所述，数据表明ts在H-ras启动子水平抑制H-ras转化。为了进一步确定ts与转录调控元件的相互作用，使用了1型人类免疫缺陷病毒（HIV-1）LTR。选择该启动子是因为它具有明确的基础转录和激活转录的调控元件，其活性受到Rep68/78基因的抑制，并且HHV-6和HIV-1在体内均自然感染CD4+ T细胞，且已证明在体外可感染同一细胞。ts抑制野生型和上游突变型HIV-1 LTR-CAT构建体的表达。然而，HIV-1 TAR下游突变逆转了ts的抑制作用，表明TAR是其中一个关键元件。所呈现的数据表明，HHV-6A ts在功能上抑制H-ras转化和HIV-1 LTR表达，因此它可能在未来的基因治疗中有用。
