Rpn13 is one of several ubiquitin receptors in the 26S proteasome. Cys88 of Rpn13 has been proposed to be the principal target of RA190, an electrophilic small molecule with interesting anti-cancer activities. Here, we examine the claim that RA190 mediates its cytotoxic effects through engagement with Rpn13. We find no evidence that this is the case. In vitro, RA190 is has no measurable effect on any of the known interactions of Rpn13. In cellulo, we see no physical engagement of Rpn13 by RA190, either on C88 or any other residue. However, chemical proteomics experiments in two different cell lines reveal that dozens of other proteins are heavily engaged by RA190. Finally, increasing or reducing the level of Rpn13 in HeLa and melanoma cells had no effect on the sensitivity of HeLa or melanoma cells to RA190. We conclude that Rpn13 is not the physiologically relevant target of RA190.

Rpn13 是 26S 蛋白酶体中的几种泛素受体之一。Rpn13 的 Cys88 被认为是 RA190 的主要靶点，RA190 是一种具有有趣抗癌活性的亲电子小分子。在这里，我们检查了 RA190 通过与 Rpn13 结合介导其细胞毒性作用的说法。我们没有发现任何证据表明情况确实如此。在体外，RA190 对 Rpn13 的任何已知相互作用没有可测量的影响。在纤维素，我们没有看到 RA190 对 Rpn13 的物理参与，无论是在 C88 还是任何其他残基上。然而，在两种不同细胞系中的化学蛋白质组学实验表明，RA190 大量参与了数十种其他蛋白质。最后，提高或降低 HeLa 和黑色素瘤细胞中 Rpn13 的水平对 HeLa 或黑色素瘤细胞对 RA190 的敏感性没有影响。我们得出结论，Rpn13 不是 RA190 的生理相关目标。