2013年10月23日，北京生命科学研究所叶克穷实验室在《RNA》杂志发表题为“Structural and functional analysis of Utp23, a yeast ribosome synthesis factor with degenerate PIN domain”的文章。
核糖体是所有生物体中合成蛋白质的巨大的分子机器，在真核生物中由4条RNA和~80个蛋白质构成。真核生物核糖体的装配也是非常复杂的过程，需要约200个保守的蛋白质因子和很多snoRNA的参与。Utp23是参与核糖体小亚基早期装配的保守的蛋白因子，它含有一个失去活性的PIN核酸酶结构域和C末端的长尾巴。
作者利用蛋白质晶体学，生物化学和酵母实验分析了Utp23的结构和功能。他们解析了Utp23 PIN结构域的2.5埃的晶体结构，发现它除了包含保守的PIN核心结构，还有一些特殊的结构——N末端额外的螺旋，C末端的延伸区域和一个锌指结构。作者还通过定点突变分析了Utp23的功能位点。他们发现螺旋1上的多个保守的碱性氨基酸残基对生长很重要，并和Utp23在体外结合RNA的活性有关。他们发现破坏锌指结构会严重的抑制酵母生长。Utp23的C末端尾巴包含一小段的保守序列，C末端的缺失能破坏Utp23和另一个核糖体装配因子snR30 RNA的结合，影响Utp23和核糖体前体的结合。该工作为理解Utp23在核糖体装配过程中的功能提供了重要的结构基础。
论文的第一作者是我所和北京协和医学院联合培养的博士研究生卢静。孙梦依同学也参与了此研究工作。叶克穷博士是本文通讯作者。此项研究受中国科技部和北京市科委资助，在北京生命科学研究所完成。(生物谷Bioon.com)
生物谷推荐的英文摘要
RNA doi:10.1261/rna.040808.113
Structural and functional analysis of Utp23, a yeast ribosome synthesis factor with degenerate PIN domain
Jing Lu, Mengyi Sun and Keqiong Ye
During synthesis of yeast ribosome, a large complex, called the 90S pre-ribosome or the small subunit processome, is assembled on the nascent precursor rRNA and mediates early processing of 18S rRNA. The Utp23 protein and snR30 H/ACA snoRNA are two conserved components of 90S pre-ribosomes. Utp23 contains a degenerate PIN nuclease domain followed by a long C-terminal tail and associates specifically with snR30. Here, we report the crystal structure of the Utp23 PIN domain at 2.5-? resolution. The structure reveals a conserved core fold of PIN domain with degenerate active site residues, a unique CCHC Zn-finger motif, and two terminal extension elements. Functional sites of Utp23 have been examined with conservation analysis, mutagenesis, and in vivo and in vitro assays. Mutations in each of three cysteine ligands of zinc, although not the histidine ligand, were lethal or strongly inhibitory to yeast growth, indicating that the Zn-finger motif is required for Utp23 structure or function. The N-terminal helix extension harbors many highly conserved basic residues that mostly are critical for growth and in vitro RNA-binding activity of Utp23. Deletion of the C-terminal tail, which contains a short functionally important sequence motif, disrupted the interaction of Utp23 with snR30 and perturbed the pre-ribosomal association of Utp23. Our data establish a structural framework for dissecting Utp23 function in the assembly and dynamics of 90S pre-ribosomes.
