Montzka K A, Steitz J A
Howard Hughes Medical Institute, Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven 06510.
Proc Natl Acad Sci U S A. 1988 Dec;85(23):8885-9. doi: 10.1073/pnas.85.23.8885.
Two-dimensional gel fractionation has revealed the existence of a number (greater than or equal to 8) of additional species of HeLa cell small RNAs that have 5' trimethylguanosine cap structures and are bound by proteins containing Sm epitopes. Therefore, these low-abundance (10(3)-10(4) per cell) RNAs belong to the Sm class of small nuclear ribonucleoproteins (snRNPs), whose best-known members are the four highly abundant (approximately 10(6) per cell) particles required for pre-mRNA splicing. The complexity of Sm snRNPs in mammalian cells is thus not greatly different from that previously established for lower eukaryotes. Two of the new RNAs, designated U11 (131 nucleotides) and U12 (150 nucleotides), have been sequenced. The U11 and U12 snRNPs have been characterized further by examining their nuclease sensitivity and their possible interactions with other snRNPs. Potential roles for the low-abundance snRNPs in aspects of pre-mRNA processing are discussed.
二维凝胶分级分离揭示了多种（大于或等于8种）额外的HeLa细胞小RNA的存在，这些小RNA具有5'三甲基鸟苷帽结构，并与含有Sm表位的蛋白质结合。因此，这些低丰度（每个细胞10³ - 10⁴个）的RNA属于小核核糖核蛋白（snRNP）的Sm类，其最著名的成员是前体mRNA剪接所需的四种高丰度（每个细胞约10⁶个）颗粒。因此，哺乳动物细胞中Sm snRNP的复杂性与先前在低等真核生物中确定的复杂性没有太大差异。已对其中两种新RNA进行了测序，分别命名为U11（131个核苷酸）和U12（150个核苷酸）。通过检测它们对核酸酶的敏感性以及它们与其他snRNP可能的相互作用，对U11和U12 snRNP进行了进一步表征。本文还讨论了低丰度snRNP在前体mRNA加工方面的潜在作用。
