Fujii T, Mimori T, Hama N, Suwa A, Akizuki M, Tojo T, Homma M
Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
J Biol Chem. 1992 Aug 15;267(23):16412-6.
We identified autoantibodies that recognize the U4/U6 snRNPs in a serum from a 63-year-old Japanese patient (TT) with primary Sjögren's syndrome. This patient's serum immunoprecipitated U4 and U6 sn-RNAs exclusively from 32P-labeled HeLa cell extracts and a newly identified 120-kDa protein along with the Sm core proteins (B'/B, D, E, F, and G) from [35S] methionine-labeled HeLa cell extracts. Immunoblotting demonstrated that only the 120-kDa protein was recognized by this unique serum. In glycerol density gradient centrifugation, the 120-kDa protein reactive with TT serum cosedimented with U4 and U6 snRNAs, suggesting that the 120-kDa protein is a unique component of the U4/U6 snRNP particle. In the same study, the U4/U6 snRNP precipitated by TT serum sedimented only in the lower density, whereas anti-Sm antibodies precipitated U4/U6 snRNAs in a broad range of the gradient. This result suggests the presence of at least two molecular forms of the U4/U6 snRNP particles; larger particles, probably the U4/U5/U6 snRNP complex, and free particles. Thus, the U4/U6 snRNP recognized by TT serum includes the U4 and U6 snRNAs, with Sm core proteins, and the novel 120-kDa protein, and appears to be a free particle not associated with larger complexes.
我们在一名63岁的日本原发性干燥综合征患者（TT）的血清中鉴定出了识别U4/U6小核核糖核蛋白颗粒（snRNPs）的自身抗体。该患者的血清仅从32P标记的HeLa细胞提取物中免疫沉淀出U4和U6小核RNA，并从[35S]甲硫氨酸标记的HeLa细胞提取物中免疫沉淀出一种新鉴定的120 kDa蛋白以及Sm核心蛋白（B'/B、D、E、F和G）。免疫印迹显示，只有这种独特的血清能识别120 kDa蛋白。在甘油密度梯度离心中，与TT血清反应的120 kDa蛋白与U4和U6小核RNA共沉降，这表明120 kDa蛋白是U4/U6 snRNP颗粒的独特成分。在同一研究中，TT血清沉淀的U4/U6 snRNP仅在较低密度处沉降，而抗Sm抗体在较宽的梯度范围内沉淀U4/U6小核RNA。这一结果表明存在至少两种分子形式的U4/U6 snRNP颗粒；较大的颗粒，可能是U4/U5/U6 snRNP复合物，以及游离颗粒。因此，TT血清识别的U4/U6 snRNP包括U4和U6小核RNA、Sm核心蛋白以及新的120 kDa蛋白，并且似乎是一种不与较大复合物相关的游离颗粒。
