Morris G E, Head L P
J Cell Sci. 1985 Jun;76:105-13. doi: 10.1242/jcs.76.1.105.
Two monoclonal antibodies, NORM and NORA, bind specifically to a 37 000 molecular weight protein in total protein extracts of chick skeletal muscle cell cultures. They have been used to follow changes in the amount and distribution of this protein during terminal differentiation and the associated cessation of cell division. Immunofluorescence microscopy shows that the antigen is found almost exclusively in the nucleolus in interphase cells and is dispersed in the cytoplasm during mitosis. Low doses of actinomycin D cause segregation of nucleoli into DNA fibrils and ribonucleoprotein granules, and the antigen is clearly associated with the latter. High doses of actinomycin D cause shrinkage of the nucleolus and the antigen is dispersed within the nucleoplasm, but not released into the cytoplasm. The amount and distribution of antigen is similar in all cell types (myoblasts, myotubes and fibroblasts) and there are no major changes during muscle differentiation. From known changes in ribosomal RNA metabolism during myogenesis and after actinomycin D treatment, we suggest that the 37 000 Mr protein is involved in some post-transcriptional aspect of ribosome production and that its concentration and distribution may be related to the concentration of ribosomal RNA in the nucleolus.
两种单克隆抗体，NORM和NORA，能特异性结合鸡骨骼肌细胞培养物总蛋白提取物中的一种分子量为37000的蛋白质。它们已被用于追踪该蛋白质在终末分化及相关细胞分裂停止过程中的数量和分布变化。免疫荧光显微镜检查显示，在间期细胞中，该抗原几乎只存在于核仁中，而在有丝分裂期间则分散在细胞质中。低剂量的放线菌素D会导致核仁分离成DNA纤维和核糖核蛋白颗粒，且该抗原明显与后者相关。高剂量的放线菌素D会导致核仁收缩，抗原分散在核质中，但不会释放到细胞质中。在所有细胞类型（成肌细胞、肌管和成纤维细胞）中，抗原的数量和分布相似，并且在肌肉分化过程中没有重大变化。根据已知的肌生成过程中及放线菌素D处理后核糖体RNA代谢的变化，我们推测这种分子量为37000的蛋白质参与了核糖体产生的某些转录后过程，其浓度和分布可能与核仁中核糖体RNA的浓度有关。
