CYTOPLASMIC ASSEMBLY OF SNRNP PARTICLES FROM STORED PROTEINS AND NEWLY TRANSCRIBED SNRNAS IN L929 MOUSE FIBROBLASTS
CYTOPLASMIC ASSEMBLY OF SNRNP PARTICLES FROM STORED PROTEINS AND NEWLY TRANSCRIBED SNRNAS IN L929 MOUSE FIBROBLASTS
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DOI：
10.1016/0014-4827(88)90336-9
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发表时间：
1988-06-01
影响因子：
3.7
通讯作者：
ZIEVE, GW
中科院分区：
文献类型：
--
作者：
SAUTERER, RA;FEENEY, RJ;ZIEVE, GW
新合成的snRNA在细胞质中短暂出现，在那里它们组装成核糖核蛋白颗粒，snRNP颗粒，然后永久返回间期核。在这份报告中，真正的细胞质组分，制备细胞去核，用于定量分析的snRNP组件在生长的小鼠成纤维细胞。在L929细胞中计算snRNP前体在细胞质中的半衰期和丰度以及snRNP组装的速率。除了U6之外，主要的snRNP是稳定的RNA种类; U1几乎完全稳定，而U2具有约两个细胞周期的半衰期。相比之下，大多数新合成的U6衰变的半衰期约为15小时。新合成的snRNA种类U1、U2、U3、U4和U6在细胞质中的相对丰度通过使用克隆探针的北方杂交测定，并且约为其核丰度的2%。细胞质中两种主要snRNA前体（U1和U2）的半衰期约为20分钟，通过标记至稳态测定。用Sm类自身抗体通过Western印迹法测定胞质中snRNP B蛋白的相对丰度，其约为核丰度的25%。动力学研究，使用Sm抗血清免疫沉淀蛋氨酸标记的snRNP蛋白，表明B蛋白在细胞质中的半衰期为90至120分钟。这些数据进行了讨论，并表明有一个大的池更稳定的snRNP蛋白质的细胞质中可用于组装的丰度较低，但更迅速地翻转的snRNA。
Newly synthesized snRNAs appear transiently in the cytoplasm where they assemble into ribonucleoprotein particles, the snRNP particles, before returning permanently to the interphase nucleus. In this report, bona fide cytoplasmic fractions, prepared by cell enucleation, are used for a quantitative analysis of snRNP assembly in growing mouse fibroblasts. The half-lives and abundances of the snRNP precursors in the cytoplasm and the rates of snRNP assembly are calculated in L929 cells. with the exception of U6, the major snRNPs are stable RNA species; U1 is almost totally stable while U2 has a half-life of about two cell cycles. In contrast, the majority of newly synthesized U6 decays with a half-life of about 15 h. The relative abundances of the newly synthesized snRNA species U1, U2, U3, U4 and U6 in the cytoplasm are determined by Northern hybridization using cloned probes and are approximately 2% of their nuclear abundance. The half-lives of the two major snRNA precursors in the cytoplasm (U1 and U2) are approximately 20 min as determined by labeling to steady state. The relative abundance of the snRNP B protein in the cytoplasm is determined by Western blotting with the Sm class of autoantibodies and is approximately 25% of the nuclear abundance. Kinetic studies, using the Sm antiserum to immunoprecipitate the methionine-labeled snRNP proteins, suggest that the B protein has a half-life of 90 to 120 min in the cytoplasm. These data are discussed and suggest that there is a large pool of more stable snRNP proteins in the cytoplasm available for assembly with the less abundant but more rapidly turning-over snRNAs.