Fury M G, Zieve G W
Department of Pathology, State University of New York, Stony Brook 11794-8691, USA.
Exp Cell Res. 1996 Oct 10;228(1):160-3. doi: 10.1006/excr.1996.0311.
The U6 snRNP is found as a monomer and as a heterodimer, complexed with the U4 snRNP (U4/U6). Northern blotting detects approximately equal amounts of U4/U6 heterodimer and U6 monomer in the nucleus but only U6 monomer in bona fide cytoplasm. In mammalian cells, newly synthesized U6 appears transiently in the cytoplasm before returning to the nucleus. Sedimentation analysis identifies cytoplasmic U6 in similarly sized structures as nuclear U4 and U6 and smaller structures than cytoplasmic U4. Inhibitor studies demonstrate that newly synthesized U6 can move from the cytoplasm into the nucleus in the absence of U4 synthesis. The nuclear half-life of U6 is significantly shorter than that of U4 and the other spliceosomal snRNAs. These data support a model in which U4 and U6 snRNAs undergo distinct cytoplasmic maturation pathways before returning to the nucleus, where the U4/U6 snRNP assembles.
U6 小核核糖核蛋白（snRNP）以单体和异二聚体形式存在，与 U4 小核核糖核蛋白（U4/U6）复合。Northern 印迹法检测到细胞核中 U4/U6 异二聚体和 U6 单体的量大致相等，但在真正的细胞质中只有 U6 单体。在哺乳动物细胞中，新合成的 U6 在返回细胞核之前会短暂出现在细胞质中。沉降分析表明，细胞质中的 U6 存在于与细胞核中的 U4 和 U6 大小相似的结构中，且比细胞质中的 U4 结构更小。抑制剂研究表明，在没有 U4 合成的情况下，新合成的 U6 可以从细胞质进入细胞核。U6 的核半衰期明显短于 U4 和其他剪接体 snRNA 的核半衰期。这些数据支持了一种模型，即 U4 和 U6 snRNA 在返回细胞核之前经历不同的细胞质成熟途径，U4/U6 snRNP 在细胞核中组装。
