A HUWE1 regulatory helix gates ASCL1 degradation through its C-terminal phospho-degron in small cell lung cancer.

A conserved regulatory helix in HUWE1 acts as an autoinhibitory gate controlling ASCL1 degradation in small cell lung cancer, with charge-flipping mutations accelerating substrate turnover.

• Why it matters: Understanding how transcription factors like ASCL1 are targeted for degradation is crucial because they are key oncogenic drivers that are difficult to inhibit directly, limiting therapeutic options in SCLC.
• What they did: Using genome-wide CRISPR knockout and base editor tiling screens combined with an endogenous reporter, the study identified HUWE1 as the main regulator of ASCL1 stability and uncovered a regulatory module within HUWE1 that modulates substrate access.
• The result: Disrupting the regulatory helix enhances degradation of substrates including ASCL1, but stabilizing ASCL1 impairs SCLC proliferation, suggesting that controlled proteasome turnover is essential for transcription factor function.