Tankyrase 1 and 2 are ADP-ribosyltransferases that catalyze formation of polyADP-Ribose (PAR) onto themselves and their binding partners. Tankyrase protein levels are regulated by the PAR-binding E3 ligase RNF146, which promotes K48-linked polyubiquitylation and proteasomal degradation of tankyrase and its partners. We identified a novel interaction between tankyrase and a distinct class of E3 ligases: the RING-UIM (Ubiquitin-Interacting Motif) family. We show that RNF114 and RNF166 bind and stabilize monoubiquitylated tankyrase and promote K11-linked diubiquitylation. This action competes with RNF146-mediated degradation, leading to stabilization of tankyrase and its binding partner, Angiomotin, a cancer cell signaling protein. Moreover, we identify multiple PAR-binding E3 ligases that promote ubiquitylation of tankyrase and induce stabilization or degradation. Discovery of K11 ubiquitylation that opposes degradation, along with identification of multiple PAR-binding E3 ligases that ubiquitylate tankyrase, provide insights into mechanisms of tankyrase regulation and may offer additional uses for tankyrase inhibitors in cancer therapy.

端锚聚合酶 1 和 2 是 ADP-核糖基转移酶，可催化在自身及其结合伴侣上形成聚 ADP-核糖 (PAR)。端锚聚合酶蛋白水平受 PAR 结合 E3 连接酶 RNF146 调节，该酶促进 K48 连接的端锚聚合酶及其伴侣的多泛素化和蛋白酶体降解。我们发现端锚聚合酶和一类独特的 E3 连接酶之间存在一种新颖的相互作用：RING-UIM（泛素相互作用基序）家族。我们发现 RNF114 和 RNF166 结合并稳定单泛素化端锚聚合酶，并促进 K11 连接的二泛素化。这种作用与 RNF146 介导的降解竞争，导致端锚聚合酶及其结合伴侣血管动蛋白（一种癌细胞信号蛋白）的稳定。此外，我们还发现了多种 PAR 结合 E3 连接酶，可促进端锚聚合酶泛素化并诱导稳定或降解。对抗降解的 K11 泛素化的发现，以及泛素化端锚聚合酶的多种 PAR 结合 E3 连接酶的鉴定，提供了对端锚聚合酶调节机制的见解，并可能为端锚聚合酶抑制剂在癌症治疗中提供其他用途。