Ruscetti S, Aurigemma R, Yuan C C, Sawyer S, Blair D G
Laboratory of Molecular Oncology, National Cancer Institute, Frederick, Maryland 21702-1201.
J Virol. 1992 Jan;66(1):20-6. doi: 10.1128/JVI.66.1.20-26.1992.
ME26 virus, which was generated by inserting the coding region of the acute avian leukemia-inducing virus E26 into a murine retrovirus vector, encodes a 135-kDa gag-myb-ets fusion protein. Amphotropic murine leukemia virus pseudotypes of ME26 virus induce a high incidence of erythroleukemia 2 to 4 months after injection into newborn NFS/N mice. Spleen cells from the majority of these mice proliferate to high levels in the presence of the erythroid hormone erythropoietin (Epo) and can easily be established as permanent Epo-dependent cell lines. The cell lines contain multiple copies of ME26 viral DNA and express viral message and protein. An Epo receptor mRNA of normal size can be detected in these cells, and binding studies reveal a single class of lower-affinity Epo receptor with an affinity for Epo that is in the range of that previously reported for erythroid cells. The ME26 virus-induced Epo-dependent cell lines, however, appear more immature than previously described erythroid cell lines and more closely resemble early hematopoietic precursor cells, suggesting that the virus may be activating the Epo receptor in hematopoietic cells that do not normally express it. Consistent with this idea, we are able to infect an interleukin-3-dependent myeloid cell line, FDC-P2, with ME26 virus and convert it to Epo dependence. The ME26 virus-infected FDC-P2 cells, even before growth on Epo, showed a large increase in the amount of Epo receptor mRNA. However, no ME26 viral integrations can be detected adjacent to the Epo receptor gene, indicating that the virus is not activating the Epo receptor gene by promoter/enhancer insertion. Our results are more consistent with the hypothesis that the gag-myb-ets-encoded viral fusion protein, which is known to bind DNA, is directly or indirectly activating the expression of the Epo receptor gene in these cells.
ME26病毒是通过将急性禽白血病诱导病毒E26的编码区插入鼠逆转录病毒载体而产生的，它编码一种135千道尔顿的gag-myb-ets融合蛋白。ME26病毒的嗜异性鼠白血病病毒假型在注射到新生NFS/N小鼠体内2至4个月后会诱发高发病率的红白血病。这些小鼠中的大多数的脾细胞在存在红系激素促红细胞生成素（Epo）的情况下会大量增殖，并且很容易被建立为永久性的依赖Epo的细胞系。这些细胞系含有多个拷贝的ME26病毒DNA，并表达病毒信息和蛋白质。在这些细胞中可以检测到正常大小的Epo受体mRNA，结合研究揭示了一类单一的低亲和力Epo受体，其对Epo的亲和力处于先前报道的红系细胞的范围内。然而，ME26病毒诱导的依赖Epo的细胞系似乎比先前描述的红系细胞系更不成熟，并且更类似于早期造血前体细胞，这表明该病毒可能在正常不表达Epo受体的造血细胞中激活了Epo受体。与此观点一致的是，我们能够用ME26病毒感染依赖白细胞介素-3的髓系细胞系FDC-P2，并将其转化为依赖Epo。即使在Epo上生长之前，被ME26病毒感染的FDC-P2细胞的Epo受体mRNA量也大幅增加。然而，在Epo受体基因附近未检测到ME26病毒整合，这表明该病毒不是通过启动子/增强子插入来激活Epo受体基因的。我们的结果与这样的假设更一致，即已知能结合DNA的gag-myb-ets编码的病毒融合蛋白在这些细胞中直接或间接激活了Epo受体基因的表达。
