Abrams H D, Rohrschneider L R, Eisenman R N
Cell. 1982 Jun;29(2):427-39. doi: 10.1016/0092-8674(82)90159-3.
The putative transforming protein of avian myelocytomatosis virus MC29 is a 110,000 dalton (P110gag-myc) polyprotein comprised of sequences derived from both the gag region and the MC29-specific myc region. Two approaches have been taken to determine the location of the MC29 gag-related proteins in transformed cells: subcellular fractionation and immunofluorescence. Analysis of subcellular fractions of MC29-transformed cells by immunoprecipitation indicates that the majority of the gag-myc polyprotein is found in the nuclear fractions of Q8 cells (a nonproducer line of MC29-transformed quail embryo fibroblasts) and nonproducer cells derived from a liver tumor of MC20-infected quail. This is in contrast to the distribution of gag-related helper virus proteins lacking myc, which are found only in nonnuclear fractions of superinfected Q8 cells. The purity of unlabeled nuclei was assessed by electron microscopy and enzyme assays, revealing little contaminating material from other subcellular fractions. Immunofluorescence experiments using monospecific anti-gag serum showed specific, intense immunofluorescence in the nuclei of fixed Q8 cells. In contrast, the majority of P75gag-erb, a candidate transforming protein produced by avian erythroblastosis virus (AEV), is absent from the nuclei of nonproducer AEV-transformed chick embryo fibroblasts. The nuclear association of the MC29 transforming protein may be related to some of the unique properties of MC29-transformed cells.
禽骨髓细胞瘤病毒MC29的假定转化蛋白是一种110,000道尔顿（P110gag-myc）的多蛋白，由来自gag区域和MC29特异性myc区域的序列组成。已采用两种方法来确定MC29 gag相关蛋白在转化细胞中的位置：亚细胞分级分离和免疫荧光。通过免疫沉淀分析MC29转化细胞的亚细胞分级分离表明，大多数gag-myc多蛋白存在于Q8细胞（MC29转化的鹌鹑胚胎成纤维细胞的非生产性系）和源自MC20感染鹌鹑肝脏肿瘤的非生产性细胞的核分级分离物中。这与缺乏myc的gag相关辅助病毒蛋白的分布形成对比，后者仅存在于超感染Q8细胞的非核分级分离物中。通过电子显微镜和酶测定评估未标记核的纯度，结果显示几乎没有来自其他亚细胞分级分离物的污染物质。使用单特异性抗gag血清的免疫荧光实验在固定的Q8细胞核中显示出特异性、强烈的免疫荧光。相比之下，禽成红细胞增多症病毒（AEV）产生的候选转化蛋白P75gag-erb在非生产性AEV转化的鸡胚成纤维细胞的细胞核中不存在。MC29转化蛋白的核关联可能与MC29转化细胞的一些独特特性有关。
