Duigou G J, Babiss L E, Iman D S, Shay J W, Fisher P B
Department of Neurological Surgery, Columbia University, College of Physicians and Surgeons, New York, New York 10032.
Mol Cell Biol. 1990 May;10(5):2027-34. doi: 10.1128/mcb.10.5.2027-2034.1990.
In the present study we have analyzed the genetic regulation of increased expression of transformation-associated traits, a process termed progression, in adenovirus type 5 (Ad5)-transformed secondary rat embryo cells. Somatic cell hybrids were formed between a highly progressed neomycin-resistant Ad5-transformed cloned cell line (E11-NMTneo) and an untransformed chloramphenicol-resistant rat embryo fibroblast cell line (CREFcap). Parental E11-NMTneo cells grew with high efficiency in agar, exhibited reduced 125I-epidermal growth factor (EGF) binding, and were tumorigenic in nude mice. Parental CREFcap cells exhibited phenotypes opposite to those of E11-NMTneo cells. A high proportion (84%) of the presumptive hybrid cell types obtained after fusion and genetic selection (G418 and chloramphenicol) displayed a flat morphological phenotype intermediate between CREFcap and E11-NMTneo cells, suggesting that a trans-dominant extinction phenomenon had occurred. Two hybrids with a round morphology (R), which still exhibited the progressed phenotype, and two hybrids with a flat morphology (F), which had lost the progressed phenotype, were chosen for detailed analysis. Both R hybrids grew efficiently in agar, exhibited low 125I-EGF binding, and were tumorigenic in nude mice, whereas both F hybrids grew poorly in agar, displayed increased 125I-EGF binding in comparison with E11-NMTneo and R hybrids, and were nontumorigenic in nude mice. An analysis of the viral DNA integration patterns and the rates of transcription, steady-state mRNA accumulation, and relative levels of the Ad5 E1A and E1B gene products revealed no differences among the parental and hybrid cells. These studies indicate that normal CREF cells may contain a suppressor gene(s) which can inhibit the expression of specific traits of the progression phenotype in Ad5-transformed cells and that this suppression is not associated with changes in the expression of Ad5 transforming genes.
在本研究中，我们分析了5型腺病毒（Ad5）转化的二代大鼠胚胎细胞中转化相关性状表达增加的遗传调控，这一过程称为进展。在一个高度进展的新霉素抗性Ad5转化克隆细胞系（E11-NMTneo）和一个未转化的氯霉素抗性大鼠胚胎成纤维细胞系（CREFcap）之间形成了体细胞杂种。亲代E11-NMTneo细胞在琼脂中高效生长，表现出降低的125I-表皮生长因子（EGF）结合能力，并且在裸鼠中具有致瘤性。亲代CREFcap细胞表现出与E11-NMTneo细胞相反的表型。融合和遗传筛选（G418和氯霉素）后获得的大部分（84%）推定杂种细胞类型呈现出介于CREFcap和E11-NMTneo细胞之间的扁平形态表型，表明发生了反式显性灭绝现象。选择了两个具有圆形形态（R）且仍表现出进展表型的杂种细胞以及两个具有扁平形态（F）且已丧失进展表型的杂种细胞进行详细分析。两个R杂种细胞在琼脂中高效生长，表现出低125I-EGF结合能力，并且在裸鼠中具有致瘤性，而两个F杂种细胞在琼脂中生长不良，与E11-NMTneo和R杂种细胞相比表现出增加的125I-EGF结合能力，并且在裸鼠中无致瘤性。对病毒DNA整合模式、转录速率、稳态mRNA积累以及Ad5 E1A和E1B基因产物的相对水平进行分析，结果显示亲代细胞和杂种细胞之间没有差异。这些研究表明，正常的CREF细胞可能含有一种抑制基因，该基因可以抑制Ad5转化细胞中进展表型的特定性状的表达，并且这种抑制与Ad5转化基因表达的变化无关。
