Neddylation-triggered ubiquitination and proteasomal degradation of HELLS inhibits prostate cancer growth via genomic instability.

Abstract

The chromatin remodeler HELLS (also known as LSH/SMARCA6) is a macromolecular regulator essential for maintaining genomic stability. Here, we identify HELLS as a critical oncogenic driver in prostate cancer and elucidate a previously unrecognized post-translational cascade that governs its protein stability. Mechanistically, we show that neddylation of HELLS primes it for subsequent ubiquitination and proteasomal degradation. The neddylation process is catalyzed by the E2 enzymes UBE2M/UBE2F in concert with an E3 ligase complex, leading to the attachment of NEDD8 to HELLS. This neddylation event then facilitates the ubiquitination of HELLS mediated by the E3 ubiquitin ligase ITCH, ultimately targeting HELLS for proteasomal turnover. Using site-directed mutagenesis, we identify K763 and K795 as the critical lysine residues for HELLS neddylation; mutation of these sites abrogates its degradation and stabilizes the protein. Leveraging this regulatory axis, we discover that the natural compound 19-Hydroxybufalin (19-HB) promotes HELLS neddylation and accelerates its ubiquitin-dependent degradation. In preclinical prostate cancer models, 19-HB treatment reduces HELLS protein levels, induces DNA damage and apoptosis, and effectively suppresses tumor growth. Collectively, our findings uncover a novel neddylation-ubiquitination cascade that controls HELLS stability and identify 19-HB as a promising natural-product-based lead for targeting this macromolecular pathway in prostate cancer.