School of Biological Sciences, Seoul National University, Seoul 08826, Korea.
Biometrology Group, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea.
Mol Cells. 2022 Jun 30;45(6):425-434. doi: 10.14348/molcells.2022.0029.
The post-translational modification (e.g., phosphorylation) of estrogen receptor α (ERα) plays a role in controlling the expression and subcellular localization of ERα as well as its sensitivity to hormone response. Here, we show that ERα is also modified by UFM1 and this modification (ufmylation) plays a crucial role in promoting the stability and transactivity of ERα, which in turn promotes breast cancer development. The elevation of ufmylation via the knockdown of UFSP2 (the UFM1-deconjugating enzyme in humans) dramatically increases ERα stability by inhibiting ubiquitination. In contrast, ERα stability is decreased by the prevention of ufmylation via the silencing of UBA5 (the UFM1-activating E1 enzyme). Lys171 and Lys180 of ERα were identified as the major UFM1 acceptor sites, and the replacement of both Lys residues by Arg (2KR mutation) markedly reduced ERα stability. Moreover, the 2KR mutation abrogated the 17β-estradiol-induced transactivity of ERα and the expression of its downstream target genes, including pS2, cyclin D1, and c-Myc; this indicates that ERα ufmylation is required for its transactivation function. In addition, the 2KR mutation prevented anchorage-independent colony formation by MCF7 cells. Most notably, the expression of UFM1 and its conjugating machinery (i.e., UBA5, UFC1, UFL1, and UFBP1) were dramatically upregulated in ERα-positive breast cancer cell lines and tissues. Collectively, these findings implicate a critical role attributed to ERα ufmylation in breast cancer development by ameliorating its stability and transactivity.
雌激素受体 α（ERα）的翻译后修饰（如磷酸化）在控制 ERα 的表达和亚细胞定位及其对激素反应的敏感性方面发挥作用。在这里，我们表明 ERα 也被 UFM1 修饰，这种修饰（ufmylation）在促进 ERα 的稳定性和转录活性方面起着至关重要的作用，进而促进乳腺癌的发展。通过敲低 UFSP2（人类中 UFM1 去连接酶）来提高 ufmylation 水平，通过抑制泛素化极大地增加了 ERα 的稳定性。相比之下，通过沉默 UBA5（UFM1-激活 E1 酶）防止 ufmylation 会降低 ERα 的稳定性。确定 ERα 的 Lys171 和 Lys180 是 UFM1 的主要接受位点，并用 Arg（2KR 突变）取代这两个赖氨酸残基会显著降低 ERα 的稳定性。此外，2KR 突变消除了 17β-雌二醇诱导的 ERα 的转录活性及其下游靶基因的表达，包括 pS2、细胞周期蛋白 D1 和 c-Myc；这表明 ERα 的 ufmylation 是其转录激活功能所必需的。此外，2KR 突变阻止了 MCF7 细胞的非锚定依赖性集落形成。最值得注意的是，在 ERα 阳性乳腺癌细胞系和组织中，UFM1 及其缀合机制（即 UBA5、UFC1、UFL1 和 UFBP1）的表达显著上调。总之，这些发现表明 ERα 的 ufmylation 通过改善其稳定性和转录活性在乳腺癌发展中起着关键作用。
