Meier U Thomas
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Chromosoma. 2005 May;114(1):1-14. doi: 10.1007/s00412-005-0333-9. Epub 2005 Mar 16.
The H/ACA ribonucleoproteins (RNPs) are known as one of the two major classes of small nucleolar RNPs. They predominantly guide the site-directed pseudouridylation of target RNAs, such as ribosomal and spliceosomal small nuclear RNAs. In addition, they process ribosomal RNA and stabilize vertebrate telomerase RNA. Taken together, the function of H/ACA RNPs is essential for ribosome biogenesis, pre-mRNA splicing, and telomere maintenance. Every cell contains 100-200 different species of H/ACA RNPs, each consisting of the same four core proteins and one function-specifying H/ACA RNA. Most of these RNPs reside in nucleoli and Cajal bodies and mediate the isomerization of specific uridines to pseudouridines. Catalysis of the reaction is mediated by the putative pseudouridylase NAP57 (dyskerin, Cbf5p). Unexpectedly, mutations in this housekeeping enzyme are the major determinants of the inherited bone marrow failure syndrome dyskeratosis congenita. This review details the many diverse functions of H/ACA RNPs, some yet to be uncovered, with an emphasis on the role of the RNP proteins. The multiple functions of H/ACA RNPs appear to be reflected in the complex phenotype of dyskeratosis congenita.
H/ACA核糖核蛋白（RNP）是已知的两类主要的小核仁核糖核蛋白之一。它们主要指导靶RNA的位点定向假尿苷化，如核糖体和剪接体小核RNA。此外，它们加工核糖体RNA并稳定脊椎动物端粒酶RNA。总之，H/ACA RNP的功能对于核糖体生物合成、前体mRNA剪接和端粒维持至关重要。每个细胞含有100 - 200种不同的H/ACA RNP，每种都由相同的四种核心蛋白和一种指定功能的H/ACA RNA组成。这些RNP大多位于核仁和卡哈尔体中，并介导特定尿苷向假尿苷的异构化。该反应的催化由推定的假尿苷酶NAP57（角化不良蛋白，Cbf5p）介导。出乎意料的是，这种管家酶的突变是遗传性骨髓衰竭综合征先天性角化不良的主要决定因素。本综述详细介绍了H/ACA RNP的多种不同功能，其中一些尚未被发现，重点是RNP蛋白的作用。H/ACA RNP的多种功能似乎反映在先天性角化不良的复杂表型中。
