A Novel tRNA Half mt‐5’‐tiRNA‐Tyr Promotes Colorectal Cancer Proliferation via Inducing HARS2 Succinylation

Transfer RNA-derived small RNAs (tsRNAs) are a novel class of small non-coding RNAs abundant in the bloodstream of cancer patients and involved in various physiological and pathological processes. However, the regulatory mechanisms and clinical significance of tsRNAs in colorectal cancer (CRC) remain unclear. In this study, PANDORA-seq was used as an exploratory screen of CRC tissues, paired adjacent tissues, and CRC plasma samples, followed by validation in larger independent cohorts. Quantitative real-time PCR quantified mt-5'-tiRNA-Tyr levels in tissues, plasma, and cells. Functional assays assessed the role of mt-5'-tiRNA-Tyr in CRC. Mechanistic studies utilized RNA pull-down, mass spectrometry, RNA immunoprecipitation, western blotting, and Co-immunoprecipitation. Results revealed that mt-5'-tiRNA-Tyr was significantly upregulated in CRC plasma and tissues. In vitro and in vivo studies demonstrated its oncogenic potential. Mechanistic assays showed that mt-5'-tiRNA-Tyr was enriched with HARS2 in RNA pull-down/RIP assays and associated with reduced HARS2-mt-tRNA-His association, increased HARS2 K91 succinylation, impaired mitochondrial protein translation, and mitochondrial damage. Moreover, succinate accumulation creates a positive feedback loop that enhances CRC proliferation. This study identifies a novel oncogenic tsRNA and uncovers a mechanism by which mt-5'-tiRNA-Tyr promotes CRC proliferation through HARS2 succinylation, supporting further evaluation of plasma mt-5'-tiRNA-Tyr as a candidate circulating biomarker for CRC.