翻译水平的调控是基因表达调控中重要的一环。绝大部分mRNAs的翻译场所可以分成内质网和胞质两大类。无论mRNAs在何处翻译，一般认为其降解场所都是在胞质或胞质的一些特殊结构中，而内质网上mRNAs被默认为结合多聚核糖体的高效翻译状态。已有研究表明，mRNAs 3’端的poly(A)尾巴的长度与mRNAs的质量控制、转运、定位、翻译效率调节和降解都密切相关，脱腺苷酸化是成熟mRNAs降解途径中的一个限速步骤。在胞质和基质中mRNAs的脱腺苷酸化和降解途径已经得到了相对深入的研究，但对于内质网上的mRNAs是否会被脱腺苷酸化这一问题还未曾受到关注。这也是本项目拟解决的核心科学问题。本项目将在初期探索的基础上，鉴定内质网上存在的主要脱腺苷酸酶以及研究其内质网定位的机制，并进一步探索内质网定位的脱腺苷酸酶是否调控了内质网mRNAs的翻译效率和所参与的细胞功能。

Regulation of translational efficiency is important to the control of eukaryotic gene expression. The bulk of mRNAs are translated on the ER surface or in the cytosol. Classically, translationally repressed mRNAs are separated from the ER and degraded or stored in the cytosol. Most mRNAs on the ER are thought to have a high translational efficiency. The poly(A) tail at the 3’-end of mRNAs have been proved to be crucial to mRNA quality control, transport, location, translational efficiency and decay. Deadenylation, the removal of the poly(A) tail, is a rate-limiting step in mRNA degradation. Although there are considerable amounts of mRNAs on the ER, it is unclear yet whether mRNAs on the ER could be deadenylated. In this research, this problem was addressed by studying deadenylases located on the ER and their potential roles in the regulation of translational efficiency of ER-localized mRNAs.