Abstract：
U6 RNA is an abundant, capped, small nuclear RNA (snRNA) species associated with heterogeneous nuclear ribonucleoproteins in eukaryotic cells. U4 RNA and U6 RNA are hydrogen bonded in a 1:1 ratio in discrete small nuclear ribonucleoprotein particles that are required in pre-mRNA processing. Previous reports have established that the mRNAs and U1 to U5 U-snRNAs are synthesized by RNA polymerase II. Evidence is presented here for synthesis of U6 RNA by RNA polymerase III. The synthesis of U6 RNA in vitro, using Novikoff hepatoma or HeLa whole cell extracts, was not inhibited at low (1 microgram/ml) concentrations of alpha-amanitin, and only 35% inhibition occurred at 10 micrograms/ml concentration. The in vitro synthesized U6 RNA, like other RNA polymerase III transcripts, was associated with La antigen. The U6 RNA synthesized in vitro by the whole cell extracts was capped, but no other internal post-transcriptional modifications were found. Uridylic acid residues were also added post-transcriptionally to the 3\'-end of U6 RNA in vitro. U6 RNA, though capped on its 5\'-end, is transcribed by RNA polymerase III; this is the first report of a capped RNA molecule synthesized by RNA polymerase III.
摘要：
U6RNA丰富，封顶,与真核细胞中异质核核糖核蛋白相关的小核RNA(snRNA)种类。U4RNA和U6RNA在前mRNA加工中所需的离散小核核糖核蛋白颗粒中以1:1的比例氢键键合。先前的报道已经确定mRNA和U1至U5U-snRNA是通过RNA聚合酶II合成的。这里提供了通过RNA聚合酶III合成U6RNA的证据。U6RNA的体外合成,使用Novikoff肝癌或HeLa全细胞提取物，在低（1微克/毫升）浓度的α-amanitin下不被抑制，在10微克/毫升浓度下仅发生35%的抑制。体外合成的U6RNA,像其他RNA聚合酶III转录物一样，与La抗原有关。将全细胞提取物体外合成的U6RNA加帽，但没有发现其他内部转录后修饰。还在体外将Urdylic酸残基转录后添加到U6RNA的3'端。U6RNA,虽然封顶在它的5'端，由RNA聚合酶III转录;这是由RNA聚合酶III合成的加帽RNA分子的首次报道。
