Molecular glues can induce proximity between a target protein and ubiquitin ligases to induce target degradation, but strategies for their discovery remain limited. We screened 3,200 bioactive small molecules and identified that C646 requires neddylation-dependent protein degradation to induce cytotoxicity. Although the histone acetyltransferase p300 is the canonical target of C646, we provide extensive evidence that C646 directly targets and degrades Exportin-1 (XPO1). Multiple cellular phenotypes induced by C646 were abrogated in cells expressing the known XPO1^C528S drug-resistance allele. While XPO1 catalyzes nuclear-to-cytoplasmic transport of many cargo proteins, it also directly binds chromatin. We demonstrate that p300 and XPO1 co-occupy hundreds of chromatin loci. Degrading XPO1 using C646 or the known XPO1 modulator S109 diminishes the chromatin occupancy of both XPO1 and p300, enabling direct targeting of XPO1 to phenocopy p300 inhibition. This work highlights the utility of drug-resistant alleles and further validates XPO1 as a targetable regulator of chromatin state.

分子胶可以诱导靶蛋白和泛素连接酶之间的接近，从而诱导靶标降解，但其发现策略仍然有限。我们筛选了 3,200 种生物活性小分子，并确定 C646 需要依赖于 neddylation 的蛋白质降解来诱导细胞毒性。尽管组蛋白乙酰转移酶 p300 是 C646 的典型靶点，但我们提供了大量证据表明 C646 直接靶向并降解 Exportin-1 (XPO1)。在表达已知 XPO1 ^C528S 耐药等位基因的细胞中，C646 诱导的多种细胞表型被消除。虽然 XPO1 催化许多货物蛋白从核到细胞质的转运，但它也直接结合染色质。我们证明 p300 和 XPO1 共同占据数百个染色质位点。使用 C646 或已知的 XPO1 调节剂 S109 降解 XPO1 可减少 XPO1 和 p300 的染色质占用率，从而能够直接靶向 XPO1 以抑制表型 p300。这项工作强调了耐药等位基因的实用性，并进一步验证了 XPO1 作为染色质状态的靶向调节剂。