Singh R, Reddy R
Baylor College of Medicine, Department of Pharmacology, Houston, TX 77030.
Proc Natl Acad Sci U S A. 1989 Nov;86(21):8280-3. doi: 10.1073/pnas.86.21.8280.
U6 small nuclear RNA (snRNA), a component of eukaryotic spliceosomes, is required for splicing of nuclear pre-mRNAs. Whereas trimethylguanosine cap-containing U sn-RNAs are transcribed by RNA polymerase II, the U6 RNA is transcribed by RNA polymerase III and contains a nonnucleotide cap structure on its 5' end. We characterized the cap structure of human U6 snRNA and show that the gamma phosphate of the 5' guanosine triphosphate is methylated. The mobilities of in vivo-modified gamma phosphate from the 5' end of HeLa U6 RNA were identical to the synthetic monomethyl phosphate (CH3-O-P) in two-dimensional chromatography and two-dimensional electrophoresis. The cap structure of U6 RNA is distinct from all other cap structures characterized thus far.
U6小核RNA（snRNA）是真核剪接体的一个组成部分，对于核内前体mRNA的剪接是必需的。含三甲基鸟苷帽的U sn - RNAs由RNA聚合酶II转录，而U6 RNA由RNA聚合酶III转录，并且在其5'端含有一个非核苷酸帽结构。我们对人U6 snRNA的帽结构进行了表征，结果表明5'鸟苷三磷酸的γ磷酸被甲基化。在二维色谱和二维电泳中，来自HeLa U6 RNA 5'端的体内修饰γ磷酸的迁移率与合成的单甲基磷酸（CH3 - O - P）相同。U6 RNA的帽结构与迄今为止所表征的所有其他帽结构都不同。
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