Hales K, Lehman J M
Exp Mol Pathol. 1987 Aug;47(1):48-58. doi: 10.1016/0014-4800(87)90006-2.
The host restriction imposed on polyoma virus by embryonal carcinoma cells can be circumvented by mutations in the enhancer region of the viral genome. In addition, expression of the early viral genes can be induced by differentiating cells transfected with purified viral DNA. Although no host-range mutants of SV40 have been isolated, expression of T antigen from episomal genomes can be induced by differentiating the embryonal carcinoma cells transfected with microgram quantities of DNA. Further, transient expression of T antigen can be observed in the embryonal carcinoma cells following transfection with large amounts of viral DNA. In addition, replication of the A2 strain of polyoma in F9 cells is enhancer dependent but the SV40 enhancer can functionally substitute for the polyoma enhancer. The F9 host-range mutant TT340 contains five tandem repeats of the region surrounding the origin of replication, and it requires T antigen for replication. The parental strain (Toronto) of the mutant is able to replicate at low levels in a T antigen-dependent manner in F9 cells. This strain also has an unselected host range for PCC4 cells and the mutation in TT340 required for growth on F9 cells does not alter this inherent host range.
胚胎癌细胞对多瘤病毒施加的宿主限制可通过病毒基因组增强子区域的突变来规避。此外，用纯化的病毒DNA转染的分化细胞可诱导早期病毒基因的表达。虽然尚未分离出SV40的宿主范围突变体，但通过分化用微克量DNA转染的胚胎癌细胞，可诱导游离基因组中T抗原的表达。此外，用大量病毒DNA转染胚胎癌细胞后，可观察到T抗原的瞬时表达。另外，多瘤病毒A2株在F9细胞中的复制依赖增强子，但SV40增强子在功能上可替代多瘤病毒增强子。F9宿主范围突变体TT340包含围绕复制起点区域的五个串联重复序列，其复制需要T抗原。该突变体的亲本菌株（多伦多株）能够以T抗原依赖的方式在F9细胞中低水平复制。该菌株对PCC4细胞也有未经选择的宿主范围，且在F9细胞上生长所需的TT340中的突变不会改变这种固有的宿主范围。
