INTRANUCLEAR MATURATION PATHWAYS OF RAT-LIVER RIBOSOMAL RIBONUCLEIC-ACIDS
INTRANUCLEAR MATURATION PATHWAYS OF RAT-LIVER RIBOSOMAL RIBONUCLEIC-ACIDS
复制标题
DOI：
10.1042/bj1600495
复制
发表时间：
1976-01-01
影响因子：
4.1
通讯作者：
TODOROV, BN
中科院分区：
文献类型：
--
作者：
DABEVA, MD;DUDOV, KP;TODOROV, BN
用琼脂/尿素凝胶电泳法、[~(14)C]转运体体内标记动力学和核糖核酸二级结构的电子显微镜观察，研究了rRNA前体在肝细胞核内的成熟过程。加工从平均分子量为4.6倍的初级前rRNA分子开始。106(45 S)，包含28 S和18 S rRNA片段。这些分子在电泳法上形成一个不均匀的峰。S的28个rRNA片段的二级结构是均一的。然而，大的转录间隔区片段(可能在5‘-末端)在大小和二级结构上是不同的。一个较小的早期标记的RNA组分，相对分子质量约5.8倍。106是可重复发现的，但其作为前rRNA物种的作用仍有待确定。确定了以下中间的前rRNA种类：3.25倍。106 mW(41 S)，两个成熟的rRNA物种共同的前体；2.60倍。106(36 S)和2.15倍。106(32 S)前驱28 S rRNA；1.05倍。106(21 S)，前身为18 S rRNA。大鼠肝脏中的前rRNA分子在大小和二级结构上与在其他哺乳动物细胞中观察到的分子相同。这些结果表明，在所有哺乳动物细胞中，前rRNA链上的内切酶裂解位点是相同的。标记动力学和36 S和21 S Pre-rRNA的同时存在表明，成年大鼠肝脏中初级Pre-rRNA的加工至少通过两条主要途径同时发生：45 S。41 S。fwdarw。32名S+21名S.Fwdarw。S 28人+S 18人，S 45人。41 S。fwdarw。S 36人+S 18人。32 S。fwdarw。28 S核糖核糖核酸。这两条途径不同的是，沿着41 S前rRNA链的内切酶攻击的时间顺序不同。一小部分(兆瓦2.9倍)。106，39 S)最有可能起源于28个S rRNA从45个S前rRNA直接分裂而来。在肝脏中，在加工过程中，前rRNA分子的裂解顺序明显存在相当大的灵活性。
The maturation of pre-rRNA (precursor to rRNA) in liver nuclei was studied by agar/urea-gel electrophoresis, kinetics of labeling in vivo with [14C]orotate and EM observation of secondary structure of RNA molecules. Processing starts from primary pre-rRNA molecules with average MW 4.6 .times. 106 (45 S) containing the segments of both 28 S and 18 S rRNA. These molecules form a heterogeneous peak on electrophoresis. The 28 S rRNA segment is homogeneous in its secondary structure. However, the large transcribed spacer segment (presumably at the 5''-end) is heterogeneous in size and secondary structure. A minor early labeled RNA component with MW about 5.8 .times. 106 is reproducibly found, but its role as a pre-rRNA species remains to be determined. The following intermediate pre-rRNA species are identified: 3.25 .times. 106 MW (41 S), a precursor common to both mature rRNA species; 2.60 .times. 106 (36 S) and 2.15 .times. 106 (32 S) precursors to 28 S rRNA; 1.05 .times. 106 (21 S) precursor to 18 S rRNA. The pre-rRNA molecules in rat liver are identical in size and secondary structure with those observed in other mammalian cells. These results suggest that the endonuclease-cleavage sites along the pre-rRNA chain are identical in all mammalian cells. Labeling kinetics and the simultaneous existence of both 36 S and 21 S pre-rRNA reveal that processing of primary pre-rRNA in adult rat liver occurs simultaneously by at least 2 major pathways: 45 S .fwdarw. 41 S .fwdarw. 32 S + 21 S.fwdarw. 28 S + 18 S rRNA and 45 S .fwdarw. 41 S .fwdarw. 36 S + 18 S .fwdarw. 32 S .fwdarw. 28 S rRNA. The 2 pathways differ by the temporal sequence of endonuclease attack along the 41 S pre-rRNA chain. A minor fraction (MW 2.9 .times. 106, 39 S) is identified as most likely originating by a direct split of 28 S rRNA from 45 S pre-rRNA. In liver considerable flexibility apparently exists in the order of cleavage of pre-rRNA molecules during processing.