Transfer RNA-derived small RNA-Gly activates the ACPH/GRHL1 axis to facilitate liver cell regeneration in acute-on chronic liver failure.

Transfer RNA (tRNA)-derived small RNAs (tsRNAs) represent a novel class of small non-coding RNAs. Our previous study showed that tsRNA exhibits differential expression patterns in patients with acute-on-chronic liver failure (ACLF), suggesting its potential as a biomarker for ACLF. Nevertheless, the precise role and underlying molecular mechanisms of tsRNA in ACLF remain largely unknown. Using small tsRNA sequencing, the present study revealed that tsRNA-Gly levels were significantly reduced in both plasma exosomes and liver tissues from patients with ACLF. Functionally, robust overexpression of tsRNA-Gly remarkably enhanced liver cell regeneration, while its downregulation inhibited this process. Mechanistically, tsRNA-Gly directly binds to the N-terminal motif domain of acylpeptide hydrolase (ACPH), a non-canonical RNA-binding protein, via a specific recognition sequence (+17-+24). This interaction stabilizes ACPH by suppressing its ubiquitin-proteasome-mediated degradation, thereby increasing its intracellular abundance. The stabilized ACPH forms a functional complex with tsRNA-Gly to activate grainy head-like 1 (GRHL1), driving its nuclear translocation and transcriptional upregulation of Cyclin D1 (CCND1) via direct promoter binding. In summary, our findings demonstrate that tsRNA-Gly serves as a critical regulator of liver regeneration through the ACPH/GRHL1/CCND1 axis. This novel discovery not only enriches our understanding of the molecular mechanisms underlying tsRNA function but also offers new insights into the role of tsRNAs in the pathogenesis of ACLF.