细胞生物学

　　人造tRNAs可诱导细胞凋亡

　　Update:2009-12-22From:JNAR Hot: 101

　　当细胞产生蛋白质的过程中出现大量的错误时，细胞的凋亡机制就会启动。但在凋亡启动之前，细胞还可以通过一些细胞的“应激应答”来挽救一部分错误。最近，巴塞罗那生物医药研究所设计了一项新方法，该方法可以用来深入研究细胞营救的信号通路和细胞的凋亡机制。这项研究发表在最新的Journal Nucleic Acids Research杂志上。

　　传统的技术是使用药物或某些化合物来干扰蛋白质合成的机器，从而产生大量的缺陷型蛋白，当细胞积累了大量的错误折叠蛋白后，细胞的报警系统被打开，细胞应激应答被激活。通过这种方法，研究人员可以观察到整个反应中的所有步骤。

　　在蛋白质的生产过程中，转运RNA(tRNA)起重要作用，能够将蛋白质合成过程中所需的氨基酸添加到蛋白质序列的合适的位置。该课题组设计了一类与天然tRNAs十分相似的全新的tRNAs，但这种tRNAs是将错误的氨基酸加到蛋白质序列中，从而导致细胞产生大量的缺陷型蛋白质，从而激活细胞的应激应答，该过程不需要引入外援的药物和化合物，可以使研究人员观察到细胞何时通过何种方式进入细胞的凋亡过程。

　　课题组通过分析表明，当细胞内积累了大量的错误折叠蛋白后，细胞还能产生一类能够调控基因表达的micro-RNAs。但目前为止，研究人员还不清楚这类micro-RNAs是如何调控基因表达过程的。

　　原始出处：

　　Nucleic Acids Research, doi:10.1093/nar/gkp1083

　　Chimeric tRNAs as tools to induce proteome damage and identify components of stress responses

　　Renaud Geslain1, Laia Cubells1, Teresa Bori-Sanz2, Roberto álvarez-Medina3, David Rossell1, Elisa Martí3 and Lluís Ribas de Pouplana1,4,*

　　1Institute for Research in Biomedicine (IRB), 2Omnia Molecular, Barcelona Science Park, 3Instituto de Biología Molecular de Barcelona, CSIC, Parc Cientific de Barcelona, c/Baldiri Reixac 15-21, Barcelona 08028 and 4Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain

　　Misfolded proteins are caused by genomic mutations, aberrant splicing events, translation errors or environmental factors. The accumulation of misfolded proteins is a phenomenon connected to several human disorders, and is managed by stress responses specific to the cellular compartments being affected. In wild-type cells these mechanisms of stress response can be experimentally induced by expressing recombinant misfolded proteins or by incubating cells with large concentrations of amino acid analogues. Here, we report a novel approach for the induction of stress responses to protein aggregation. Our method is based on engineered transfer RNAs that can be expressed in cells or tissues, where they actively integrate in the translation machinery causing general proteome substitutions. This strategy allows for the introduction of mutations of increasing severity randomly in the proteome, without exposing cells to unnatural compounds. Here, we show that this approach can be used for the differential activation of the stress response in the Endoplasmic Reticulum (ER). As an example of the applications of this method, we have applied it to the identification of human microRNAs activated or repressed during unfolded protein stress.