Departments of Developmental Biology and Pharmacology, University of Texas Southwestern Medical Center at Dallas, TX 75390, USA.
Proc Natl Acad Sci U S A. 2009 Dec 15;106(50):21191-6. doi: 10.1073/pnas.0912008106. Epub 2009 Dec 2.
The Cul3-based E3 ubiquitin ligases regulate many cellular processes using a large family of BTB domain-containing proteins as their target recognition components, but how they recognize targets remains unknown. Here we identify and characterize degrons that mediate the degradation of the Hedgehog pathway transcription factor cubitus interruptus (Ci)/Gli by Cul3-Hedghog-induced MATH and BTB domain-containing protein (HIB)/SPOP. Ci uses multiple Ser/Thr (S/T)-rich motifs that bind HIB cooperatively to mediate its degradation. We provide evidence that both HIB and Ci form dimers/oligomers and engage in multivalent interactions, which underlies the in vivo cooperativity among individual HIB-binding sites. We find that similar S/T-rich motifs are present in Gli proteins as well as in numerous HIB-interacting proteins and mediate Gli degradation by SPOP. Our results provide a mechanistic insight into how HIB/SPOP recognizes its substrates and have important implications for the genome-wide prediction of substrates for Cul3-based E3 ligases.
基于 Cul3 的 E3 泛素连接酶利用一大类含有 BTB 结构域的蛋白质作为其靶标识别组件来调节许多细胞过程，但它们如何识别靶标仍然未知。在这里，我们鉴定并表征了介导 Hedgehog 途径转录因子 cubitus interruptus (Ci)/Gli 降解的降解信号，该降解信号由 Cul3-Hedgehog 诱导的 MATH 和 BTB 结构域含有蛋白 (HIB)/SPOP 介导。Ci 使用多个富含丝氨酸/苏氨酸 (S/T) 的基序与 HIB 协同结合来介导其降解。我们提供的证据表明，HIB 和 Ci 均形成二聚体/寡聚体并进行多价相互作用，这是体内单个 HIB 结合位点之间协同作用的基础。我们发现 Gli 蛋白以及许多与 HIB 相互作用的蛋白中都存在类似的 S/T 富含基序，并通过 SPOP 介导 Gli 降解。我们的研究结果提供了 Cul3 基 E3 连接酶识别其底物的机制见解，并对基于基因组范围预测 Cul3 基 E3 连接酶的底物具有重要意义。
