Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan.
Department of Computational Biology and Medical Sciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba-ken 277-8651, Japan.
J Mol Biol. 2017 Oct 27;429(21):3319-3333. doi: 10.1016/j.jmb.2017.04.017. Epub 2017 May 3.
Trinucleotide repeat-containing gene 6A protein (TNRC6A) is an essential protein for microRNA-mediated gene silencing. TNRC6A functions in the cytoplasm as a platform protein interacting with Argonaute protein, on which microRNA is loaded for RNA silencing, and decapping enzymes or deadenylation protein complexes to induce mRNA degradation. We previously revealed that TNRC6A shuttles between the cytoplasm and nucleus. However, the function of TNRC6A in the nucleus is unclear. Here, we performed a comprehensive identification of the nuclear and cytoplasmic interacting proteins of TNRC6A protein by mass spectrometry and identified multiple proteins involved in the nuclear and cytoplasmic complexes. We found that many RNA degradation pathway proteins were involved in both nuclear and cytoplasmic TNRC6A complexes, suggesting that RNA silencing may occur via TNRC6A in both nucleus and cytoplasm or that they were involved in other important function in the nucleus. Furthermore, proteins identified in the nuclear TNRC6A complex were categorized into the spliceosomal pathway. This may mean that TNRC6A regulates splicing in the nucleus. In contrast, pathogen infection- and RNA transport-associated proteins were identified in the cytoplasmic TNRC6A complex. Thus, TNRC6A may be also involved in these pathways in the cytoplasm.
三核苷酸重复基因 6A 蛋白（TNRC6A）是 microRNA 介导的基因沉默所必需的蛋白。TNRC6A 在细胞质中作为一种平台蛋白发挥作用，与 Argonaute 蛋白相互作用，microRNA 加载到 Argonaute 蛋白上进行 RNA 沉默，与脱帽酶或去腺苷酸化蛋白复合物一起诱导 mRNA 降解。我们之前发现 TNRC6A 在细胞质和细胞核之间穿梭。然而，TNRC6A 在细胞核中的功能尚不清楚。在这里，我们通过质谱法对 TNRC6A 蛋白的核内和胞质内相互作用蛋白进行了全面鉴定，鉴定出了多个参与核内和胞质复合物的蛋白质。我们发现，许多 RNA 降解途径蛋白参与核内和胞质 TNRC6A 复合物，这表明 RNA 沉默可能通过核内和胞质中的 TNRC6A 发生，或者它们参与细胞核中的其他重要功能。此外，在核 TNRC6A 复合物中鉴定到的蛋白质被归类为剪接体途径。这可能意味着 TNRC6A 调节细胞核中的剪接。相比之下，在细胞质 TNRC6A 复合物中鉴定到了与病原体感染和 RNA 转运相关的蛋白质。因此，TNRC6A 可能也参与了细胞质中的这些途径。
