Deng Wentao, Vanderbilt Daniel B, Lin Chen-Chung, Martin Karen H, Brundage Kathleen M, Ruppert J Michael
The Department of Biochemistry, West Virginia University, Morgantown, West Virginia 26506 The Mary Babb Randolph Cancer Center, West Virginia University, West Virginia 26506.
Program in Cancer Cell Biology, West Virginia University, Morgantown, West Virginia 26506.
J Cell Sci. 2015 Mar 15;128(6):1123-38. doi: 10.1242/jcs.162164. Epub 2015 Jan 27.
The high mobility group box protein SOX9 and the GLI1 transcription factor play protumorigenic roles in pancreatic ductal adenocarcinoma (PDA). In Kras transgenic mice, each of these factors are crucial for the development of PDA precursor lesions. SOX9 transcription is directly regulated by GLI1, but how SOX9 functions downstream of GLI1 is unclear. We observed positive feedback, such that SOX9-deficient PDA cells have severely repressed levels of endogenous GLI1, attributed to loss of GLI1 protein stability. SOX9 associated with the F-box domain of the SKP1/CUL1/F-box (SCF) E3 ubiquitin ligase component, β-TrCP (also known as F-box/WD repeat-containing protein 1A), and suppressed its association with SKP1 and GLI1, a substrate of SCF-β-TrCP. SOX9 also tethered β-TrCP within the nucleus and promoted its degradation. SOX9 bound to β-TrCP through the SOX9 C-terminal PQA/S domain that mediates transcriptional activation. Suppression of β-TrCP in SOX9-deficient PDA cells restored GLI1 levels and promoted SOX9-dependent cancer stem cell properties. These studies identify SOX9-GLI1 positive feedback as a major determinant of GLI1 protein stability and implicate β-TrCP as a latent SOX9-bound tumor suppressor with the potential to degrade oncogenic proteins in tumor cells.
高迁移率族蛋白盒蛋白SOX9和GLI1转录因子在胰腺导管腺癌（PDA）中发挥促肿瘤作用。在Kras转基因小鼠中，这些因子中的每一个对于PDA前体病变的发展都至关重要。SOX9转录直接受GLI1调控，但SOX9在GLI1下游如何发挥作用尚不清楚。我们观察到正反馈，即SOX9缺陷的PDA细胞中内源性GLI1水平受到严重抑制，这归因于GLI1蛋白稳定性的丧失。SOX9与SKP1/CUL1/F-box（SCF）E3泛素连接酶组分β-TrCP（也称为含F-box/WD重复蛋白1A）的F-box结构域相关联，并抑制其与SKP1和SCF-β-TrCP的底物GLI1的结合。SOX9还将β-TrCP束缚在细胞核内并促进其降解。SOX9通过介导转录激活的SOX9 C末端PQA/S结构域与β-TrCP结合。在SOX9缺陷的PDA细胞中抑制β-TrCP可恢复GLI1水平并促进SOX9依赖的癌症干细胞特性。这些研究确定SOX9-GLI1正反馈是GLI1蛋白稳定性的主要决定因素，并表明β-TrCP是一种潜在的与SOX9结合的肿瘤抑制因子，具有降解肿瘤细胞中致癌蛋白的潜力。
