Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37232, USA.
Department of Molecular and Systems Biology and the Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth College, Hanover, NH 03755, USA.
Sci Signal. 2023 Feb 7;16(771):eabn8372. doi: 10.1126/scisignal.abn8372.
The Wnt-β-catenin signal transduction pathway is essential for embryonic development and adult tissue homeostasis. Wnt signaling converts TCF from a transcriptional repressor to an activator in a process facilitated by the E3 ligase XIAP. XIAP-mediated monoubiquitylation of the transcriptional corepressor Groucho (also known as TLE) decreases its affinity for TCF, thereby allowing the transcriptional coactivator β-catenin to displace it on TCF. Through a genome-scale screen in cultured cells, we identified the deubiquitylase USP47 as a positive regulator of Wnt signaling. We found that USP47 was required for Wnt signaling during and development, as well as in human cells, indicating evolutionary conservation. In human cells, knockdown of USP47 inhibited Wnt reporter activity, and USP47 acted downstream of the β-catenin destruction complex. USP47 interacted with TLE3 and XIAP but did not alter their amounts; however, knockdown of USP47 enhanced XIAP-mediated ubiquitylation of TLE3. USP47 inhibited ubiquitylation of TLE3 by XIAP in vitro in a dose-dependent manner, suggesting that USP47 is the deubiquitylase that counteracts the E3 ligase activity of XIAP on TLE. Our data suggest a mechanism by which regulated ubiquitylation and deubiquitylation of TLE enhance the ability of β-catenin to cycle on and off TCF, thereby helping to ensure that the expression of Wnt target genes continues only as long as the upstream signal is present.
Wnt-β-catenin 信号转导通路对于胚胎发育和成人组织稳态至关重要。Wnt 信号通过 E3 连接酶 XIAP 将 TCF 从转录抑制剂转化为激活剂。XIAP 介导的转录共抑制因子 Groucho（也称为 TLE）的单泛素化降低了其与 TCF 的亲和力，从而允许转录共激活因子 β-catenin 在 TCF 上取代它。通过在培养细胞中的全基因组筛选，我们鉴定出去泛素化酶 USP47 是 Wnt 信号的正向调节剂。我们发现 USP47 在 和 发育过程中以及在人类细胞中都需要 Wnt 信号，表明其具有进化保守性。在人类细胞中，USP47 的敲低抑制了 Wnt 报告基因的活性，并且 USP47 作用于 β-catenin 破坏复合物的下游。USP47 与 TLE3 和 XIAP 相互作用，但不改变它们的含量；然而，USP47 的敲低增强了 XIAP 介导的 TLE3 的泛素化。USP47 以剂量依赖的方式在体外抑制 XIAP 介导的 TLE3 的泛素化，表明 USP47 是拮抗 XIAP 对 TLE 的 E3 连接酶活性的去泛素化酶。我们的数据提出了一种机制，即 TLE 的调节泛素化和去泛素化增强了 β-catenin 在 TCF 上循环的能力，从而有助于确保 Wnt 靶基因的表达仅在存在上游信号时继续。
