Choubey D, Lengyel P
Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
J Cell Biol. 1992 Mar;116(6):1333-41. doi: 10.1083/jcb.116.6.1333.
The interferons are cytokines with antiviral, cell growth regulatory, and immunomodulatory activities. These activities are mediated by the proteins induced by the interferons. Earlier we described a gene cluster (the 200 cluster) consisting of at least six adjacent, interferon-activatable genes located next to the erythroid alpha-spectrin locus on murine chromosome 1. The genes of the cluster arose by repeated gene duplication and they specify proteins with pronounced sequence similarity. We have now raised polyclonal antibodies against a segment from one of these proteins (the 204 protein of 72 kD). Using these, we established that the 204 protein is a phosphoprotein whose level in cells from various murine lines can be increased up to 75-fold upon treatment with alpha interferon. Experiments involving fractionation of cell lysates and indirect immunofluorescence microscopy of control and interferon-treated cells revealed that the 204 protein is nucleolar and nucleoplasmic. This conclusion was confirmed by co-localization with B23, a known nucleolar protein. The 204 protein is the first interferon-induced protein found to be located in the nucleoli, the subcellular organelles of ribosomal RNA production and ribosome assembly. It remains to be seen whether the 204 protein affects any of these processes. Studies on 204 protein function should be facilitated by the availability of complete cDNA clones and the finding of cell lines in which the expression of this protein is impaired.
干扰素是一类具有抗病毒、细胞生长调节和免疫调节活性的细胞因子。这些活性由干扰素诱导产生的蛋白质介导。此前我们描述了一个基因簇（200 基因簇），它由至少六个相邻的、可被干扰素激活的基因组成，位于小鼠 1 号染色体上的红细胞α-血影蛋白基因座旁边。该基因簇中的基因通过重复基因复制产生，它们编码的蛋白质具有明显的序列相似性。我们现在制备了针对其中一种蛋白质（72 kD 的 204 蛋白）的一段序列的多克隆抗体。利用这些抗体，我们确定 204 蛋白是一种磷蛋白，在用α干扰素处理后，来自不同小鼠品系的细胞中该蛋白的水平可增加多达 75 倍。对细胞裂解物进行分级分离以及对对照细胞和经干扰素处理的细胞进行间接免疫荧光显微镜观察的实验表明，204 蛋白存在于核仁和核质中。与已知的核仁蛋白 B23 共定位证实了这一结论。204 蛋白是首个被发现定位于核仁的干扰素诱导蛋白，核仁是核糖体 RNA 产生和核糖体组装的亚细胞细胞器。204 蛋白是否会影响这些过程还有待观察。完整 cDNA 克隆的可得性以及该蛋白表达受损的细胞系的发现将有助于对 204 蛋白功能的研究。
