Accurate pre-mRNA splicing is needed for correct gene expression and relies on faithful splice site recognition. Here, we show that the ubiquitin-like protein Hub1 binds to the DEAD-box helicase Prp5, a key regulator of early spliceosome assembly, and stimulates its ATPase activity thereby enhancing splicing and relaxing fidelity. High Hub1 levels enhance splicing efficiency but also cause missplicing by tolerating suboptimal splice sites and branchpoint sequences. Notably, Prp5 itself is regulated by a Hub1-dependent negative feedback loop. Since Hub1-mediated splicing activation induces cryptic splicing of Prp5, it also represses Prp5 protein levels and thus curbs excessive missplicing. Our findings indicate that Hub1 mediates enhanced, but error-prone splicing, a mechanism that is tightly controlled by a feedback loop of PRP5 cryptic splicing activation.

正确的mRNA前剪接对于正确的基因表达是必需的，并且依赖于忠实的剪接位点识别。在这里，我们显示泛素样蛋白Hub1与DEAD-box解旋酶Prp5（早期剪接体装配的关键调节剂）结合，并刺激其ATPase活性，从而增强剪接和保真度。Hub1高水平可提高剪接效率，但由于容许次优剪接位点和分支点序列，也会导致错配。值得注意的是，Prp5本身由依赖Hub1的负反馈环路调节。由于Hub1介导的剪接激活诱导了Prp5的隐式剪接，因此它也抑制了Prp5的蛋白水平，从而抑制了过多的错配。我们的发现表明，Hub1介导了增强的但易错的剪接，该机制受反馈环的严格控制。PRP5隐式拼接激活。