Human RNA ligase 1 as a novel regulator of ribosome function and translation under oxidative stress.

Human RNA ligase 1 (Rlig1) is a recently identified human 5'-3' RNA ligase required for maintaining 28S ribosomal RNA integrity and promoting cell survival under oxidative stress. Although its enzymatic activity suggests a role in RNA processing and repair, the broader molecular context of Rlig1 remains poorly defined. Here, we identified potential Rlig1-associated proteins by affinity enrichment-mass spectrometry. Subsequent analysis revealed proteins involved in RNA surveillance and processing, including RNA-binding and end-processing enzymes, and indicated strong enrichment of ribosomal proteins. We showed that Rlig1 interacts with 80S ribosomes in vitro. Consistent with this observation, polysome profiling revealed recruitment of Rlig1 to ribosomal fractions under oxidative stress. Functionally, Rlig1-knockout (KO) HEK293 cells exhibited accelerated polysome loss and significantly reduced global protein synthesis compared to wild-type (WT) HEK293 cells during oxidative stress. In addition, we showed that stress-induced RNA fragments containing a 5'-PO4 end accumulated in Rlig1-KO cells. Among these, transfer RNA halves were prominently enriched. Together, our study links Rlig1 to ribosomal complexes and suggests that Rlig1 contributes to preserving RNA integrity and supporting translational capacity during oxidative stress.