Regulating the amount of proteins in living cells is a powerful approach for understanding the functions of the proteins. Immunomodulatory drugs (IMiDs) induce the degradation of neosubstrates by interacting with celebron (CRBN) in the cullin E3 ubiquitin ligase complex (CRL4^CRBN). Here, we developed the IMiD-dependent Sal-like protein 4 (SALL4) degron (S4D) system for chemical protein knockdown. In transient assays, an N- or C-terminal S4D tag induced the degradation of proteins localized to various subcellular compartments, including the plasma membrane. The activity of luciferase-S4D was reduced by 90% within 3 h of IMiD treatment. IMiD treatment reduced the expression of endogenous S4D-fused RelA and IκBα in knock-in (KI) experiments. Interestingly, the IκBα knockdown suggested that there may be another, unknown mechanism for RelA translocation to the nucleus. Furthermore, 5-hydroxythalidomide as a thalidomide metabolite specifically degradated S4D-tagged protein. These results indicate that the S4D system is a useful tool for cellular biology.

调节活细胞中蛋白质的数量是了解蛋白质功能的有效方法。免疫调节药物 (IMiD) 通过与 cullin E3 泛素连接酶复合物 (CRL4 ^CRBN ) 中的 celebron (CRBN) 相互作用诱导新底物降解）。在这里，我们开发了 IMiD 依赖性 Sal 样蛋白 4 (SALL4) degron (S4D) 系统，用于化学蛋白敲除。在瞬时测定中，N 或 C 末端 S4D 标签诱导定位于各种亚细胞区室（包括质膜）的蛋白质降解。IMiD 处理后 3 小时内，荧光素酶-S4D 的活性降低了 90%。在敲入 (KI) 实验中，IMiD 处理降低了内源性 S4D 融合的 RelA 和 IκBα 的表达。有趣的是，IκBα 敲低表明 RelA 易位至细胞核可能存在另一种未知机制。此外，5-羟基沙利度胺作为沙利度胺代谢物可特异性降解 S4D 标记蛋白。这些结果表明 S4D 系统是细胞生物学的有用工具。