摘要
无义介导的mRNA降解途径(nonsense-mediated mRNA decay,NMD)作为细胞内的一种重要的mRNA质量监控机制,可以降解含有提前终止密码子(premature termination codon,PTC)的异常转录本,从而避免截短蛋白质对细胞的毒害,但其详细的分子机制有待进一步阐释。蓝氏贾第虫(Giardia lamblia)作为一种寄生性单细胞原生动物,进化地位特殊,对其NMD途径的研究有利于阐明基因表达调控的分子和进化机制。本研究通过酵母双杂交及体外pull-down实验分析了贾第虫NMD途径因子上游移码蛋白1 (Giardia lamblia up-frameshift 1,Gl UPF1)、贾第虫RNA结合蛋白(Giardia lamblia HRP1,Gl HRP1)、贾第虫核糖核酸外切酶(Giardia lamblia Ski7p,Gl Ski7p、Giardia lamblia XRN1,Gl XRN1)之间的相互作用关系。结果表明,Gl UPF1全长与Gl HRP1、Gl XRN1(1~500aa)、Gl Ski7p间均可发生相互作用。而且Gl UPF1的CH结构域和C端结构域分别与Gl HRP1、Gl XRN1(1~500 aa)、Gl Ski7p相互作用。说明Gl UPF1在贾第虫NMD途径中作为招募平台,在无义mRNA识别和降解过程中发挥重要作用。为此,结合本实验室之前的研究结果,我们提出原生动物贾第虫的NMD途径:在提前终止密码子处SURF(SMG1-UPF1-eRF1-eRF3)复合物形成后,Gl UPF1被磷脂酰肌醇3-激酶(suppressor with morphogenetic effect on genitalia 1,SMG1)磷酸化修饰,NMD途径激活,随后Gl UPF1与HRP1相互作用,将转录本标记为NMD底物; Gl UPF1进而招募下游贾第虫5'-3'核糖核酸降解酶Gl XRN1、贾第虫3'-5'核糖核酸降解因子Gl Ski7p,最终降解靶标mRNA。
Nonsense-mediated mRNA decay( NMD),as an important mRNA quality-control mechanism in cells,can distinguish and degrade aberrant transcripts with premature termination codons( PTCs) to avoid production of truncated toxic proteins. However,its detailed mechanism is not fully understood.Giardia lamblia is a kind of parasitic unicellular protozoan with special evolutionary status. The study on NMD of G. lamblia can help us elucidate the mechanism and evolution of gene expression. In this study,the interaction between the NMD core factor Giardia lamblia up-frameshift protein 1( Gl UPF1),RNAbinding protein( Gl HRP1) and exoribonuclease Gl XRN1,Gl Ski7 p were confirmed by yeast two-hybrid assays and in vitro pull-down experiments. The results showed that the full-length Gl UPF1 could interact with Gl HRP1,Gl XRN1 and Gl Ski7 p. The CH domain and C termination domain could also interact with Gl HRP1,Gl XRN1( 1-500 aa) and Gl Ski7 p. This demonstrated that Gl UPF1 as a recruiting platform in the NMD pathway played an important role in distinguishing and degrading nonsense transcripts.Combined with the previous research results of this laboratory,we proposed a NMD pathway in the protozoan G. lamblia: the SURF( SMG1-UPF-eRF1-eRF3) complex was first formed on PTC-mRNA,then the Gl UPF1 was phosphorylated by PI3 K-related kinase 1 Gl SMG1 and the NMD pathway was activated. Next,interaction between Gl UPF1 and Gl HRP1 marked transcripts as an NMD target,then Gl UPF1 recruited 5’-3’ exoribonuclease Gl XRN1 and 3’-5’ exoribonuclease Gl Ski7 p to degrade aberrant transcripts.
作者
吕佳
柴杨丽
周宝春
柴宝峰
LV Jia;CHAI Yang-Li;ZHOU Bao-Chun;CHAI Bao-Feng(Key Laboratory of Chemical Biology and Molecular Engineering,Ministry of Education,Institute of Biotechnology, Shanxi University,Taiyuan 030006,China)
出处
《中国生物化学与分子生物学报》
CAS
CSCD
北大核心
2019年第2期212-221,共10页
Chinese Journal of Biochemistry and Molecular Biology
基金
国家自然科学基金(No.31772450)
山西省科技攻关项目(No.20150313001-3)资助~~
关键词
蓝氏贾第虫
无义介导的mRNA降解途径
贾第虫不均一核小核糖核蛋白
贾第虫上游移码蛋白1
贾第虫5’-3’核糖核酸外切酶
贾第虫3’-5’超级杀手蛋白质
Giardia lamblia
nonsense-mediated mRNA decay pathway (NMD)
Giardia lamblia heterogeneous nuclear ribonucleoprotein 1 (GlHRP1)
Giardia lamblia up-frameshift protein 1 (GlUPF 1 )
Giardia lamblia 5'-3'exoribonuclease 1 (GlXRN 1 )
Giardia lamblia 3'-5'superkiller protein 7 (GlSki7p)