Yoshida Madoka, Yoshida Kaori, Kozlov Guennadi, Lim Nadia S, De Crescenzo Gregory, Pang Zhiyu, Berlanga Juan Jose, Kahvejian Avak, Gehring Kalle, Wing Simon S, Sonenberg Nahum
Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
EMBO J. 2006 May 3;25(9):1934-44. doi: 10.1038/sj.emboj.7601079. Epub 2006 Apr 6.
The poly(A)-binding protein (PABP) is a unique translation initiation factor in that it binds to the mRNA 3' poly(A) tail and stimulates recruitment of the ribosome to the mRNA at the 5' end. PABP activity is tightly controlled by the PABP-interacting protein 2 (Paip2), which inhibits translation by displacing PABP from the mRNA. Here, we describe a close interplay between PABP and Paip2 protein levels in the cell. We demonstrate a mechanism for this co-regulation that involves an E3 ubiquitin ligase, EDD, which targets Paip2 for degradation. PABP depletion by RNA interference (RNAi) causes co-depletion of Paip2 protein without affecting Paip2 mRNA levels. Upon PABP knockdown, Paip2 interacts with EDD, which leads to Paip2 ubiquitination. Supporting a critical role for EDD in Paip2 degradation, knockdown of EDD expression by siRNA leads to an increase in Paip2 protein stability. Thus, we demonstrate that the turnover of Paip2 in the cell is mediated by EDD and is regulated by PABP. This mechanism serves as a homeostatic feedback to control the activity of PABP in cells.
聚腺苷酸结合蛋白（PABP）是一种独特的翻译起始因子，它能与mRNA的3' 聚腺苷酸尾结合，并促进核糖体在5' 端与mRNA的结合。PABP的活性受到与PABP相互作用蛋白2（Paip2）的严格调控，Paip2通过将PABP从mRNA上置换下来来抑制翻译。在此，我们描述了细胞中PABP和Paip2蛋白水平之间的密切相互作用。我们展示了一种涉及E3泛素连接酶EDD的共同调节机制，EDD将Paip2作为降解靶点。通过RNA干扰（RNAi）使PABP缺失会导致Paip2蛋白共同缺失，而不影响Paip2的mRNA水平。PABP敲低后，Paip2与EDD相互作用，导致Paip2泛素化。支持EDD在Paip2降解中起关键作用的是，通过小干扰RNA（siRNA）敲低EDD表达会导致Paip2蛋白稳定性增加。因此，我们证明细胞中Paip2的周转由EDD介导，并受PABP调控。这种机制作为一种稳态反馈来控制细胞中PABP的活性。
