Aspartyl-tRNA synthetase 1 (DARS1) reshapes hepatocellular carcinoma proteome and promotes aggressiveness through non-canonical SAGA–MYC signalling modulation

BACKGROUND: Aminoacyl-tRNA synthetases (ARSs) exert canonical and emerging non-canonical roles in cancer. Given the frequent alterations in aspartate metabolism in hepatocellular carcinoma (HCC), we investigated the clinical and functional significance of aspartyl-tRNA synthetase (DARS1) in HCC. METHODS: DARS1 expression was evaluated in tumor and matched non-tumoral tissues, in silico cohorts, and plasma samples. Functional assays were performed in liver cancer cell lines after genetic and pharmacological modulation of DARS1. In vivo validation was conducted using xenograft and orthotopic tumor models. Protein interactors of DARS1 were characterized by quantitative proteomics and confirmed by biochemical approaches. RESULTS: DARS1 abundance was increased in HCC, especially in highly aggressive tumours, and in plasma from HCC patients. DARS1 overexpression increased aggressiveness in vitro and xenograft and orthotopic tumour formation in vivo, while genetic and pharmacological blockade of DARS1 impaired stemness in vitro without affecting normal-like cells. Proteomic profiling revealed a significant enrichment of high-aspartate proteins in DARS1-overexpressing cells, demonstrating a reshaping of the HCC proteome. Beyond its canonical role, DARS1 was found in the nucleus interacting with members of the SAGA transcriptional co-activator complex, including SUPT7L. This interaction affected MYC regulation, as DARS1 depletion reduced MYC protein levels, increased its phosphorylation, and enhanced drug-induced senescence, linking DARS1-SAGA activity to MYC-driven oncogenic pathways. CONCLUSIONS: DARS1 is frequently overexpressed in HCC and detectable in plasma, supporting its potential as liquid biopsy biomarker. Functionally, DARS1 represents a novel vulnerability of HCC, acting through both proteome reshaping and non-canonical nuclear interactions with the SAGA complex that modulate MYC activity.