MYC-driven BYSL overexpression promotes hepatocellular carcinoma by suppressing nucleolar stress and inactivating the RPL5/RPL11-MDM2-p53 pathway.

BYSL gene encodes the bystin-like (BYSL) protein, a nucleolar protein involved in eukaryotic ribosome biogenesis and essential for 40S ribosomal subunit synthesis. Although BYSL upregulation has been implicated in hepatocellular carcinoma, its mechanistic contribution to tumor progression remains undefined. We observed that BYSL is consistently upregulated across multiple cancer types and is associated with adverse clinicopathological features and poor prognosis, with the strongest clinical relevance observed in hepatocellular carcinoma through the integrative transcriptomic and proteomic analyses. BYSL-knockout suppresses malignant phenotypes, including proliferation, migration, and invasion, and induced G1/S arrest and apoptosis. Mechanistically, loss of BYSL disrupts nucleolar homeostasis and reduces global protein synthesis, thereby activating the RPL5/RPL11-MDM2-p53 axis, leading to p53 stabilization and tumor suppression. Importantly, MYC directly bound to the BYSL promoter and transcriptionally activated its expression, whereas co-targeting BYSL and MYC produced more synergistic antitumor effects than either intervention alone. Collectively, our study reveals that BYSL acts as a pivotal downstream mediator of MYC-regulated ribosome biogenesis and promotes hepatocellular carcinoma progression. Our findings suggest that BYSL may represent a potential therapeutic target for hepatocellular carcinoma; nevertheless, additional in vivo preclinical studies are warranted to validate its translational prospects.