Developmental and Molecular Pathways, Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, USA.
Nat Cell Biol. 2011 May;13(5):623-9. doi: 10.1038/ncb2222. Epub 2011 Apr 10.
The Wnt/β-catenin signalling pathway plays essential roles in embryonic development and adult tissue homeostasis, and deregulation of this pathway has been linked to cancer. Axin is a concentration-limiting component of the β-catenin destruction complex, and its stability is regulated by tankyrase. However, the molecular mechanism by which tankyrase-dependent poly(ADP-ribosyl)ation (PARsylation) is coupled to ubiquitylation and degradation of axin remains undefined. Here, we identify RNF146, a RING-domain E3 ubiquitin ligase, as a positive regulator of Wnt signalling. RNF146 promotes Wnt signalling by mediating tankyrase-dependent degradation of axin. Mechanistically, RNF146 directly interacts with poly(ADP-ribose) through its WWE domain, and promotes degradation of PARsylated proteins. Using proteomics approaches, we have identified BLZF1 and CASC3 as further substrates targeted by tankyrase and RNF146 for degradation. Thus, identification of RNF146 as a PARsylation-directed E3 ligase establishes a molecular paradigm that links tankyrase-dependent PARsylation to ubiquitylation. RNF146-dependent protein degradation may emerge as a major mechanism by which tankyrase exerts its function.
Wnt/β-连环蛋白信号通路在胚胎发育和成人组织稳态中发挥着重要作用，该通路的失调与癌症有关。轴蛋白是β-连环蛋白降解复合物的浓度限制组成部分，其稳定性受 Tankyrase 调节。然而，Tankyrase 依赖性聚（ADP-核糖）化（PARsylation）与轴蛋白泛素化和降解偶联的分子机制尚不清楚。在这里，我们鉴定出 RNF146 是一种 RING 结构域 E3 泛素连接酶，是 Wnt 信号的正向调节剂。RNF146 通过介导 Tankyrase 依赖性轴蛋白降解来促进 Wnt 信号。在机制上，RNF146 通过其 WWE 结构域直接与多聚（ADP-核糖）相互作用，并促进 PARsylated 蛋白的降解。使用蛋白质组学方法，我们已经鉴定出 BLZF1 和 CASC3 是 Tankyrase 和 RNF146 用于降解的进一步底物。因此，将 RNF146 鉴定为 PARsylation 定向的 E3 连接酶，建立了一个分子范例，将 Tankyrase 依赖性 PARsylation 与泛素化联系起来。RNF146 依赖性蛋白降解可能成为 Tankyrase 发挥其功能的主要机制。
