Identification of a Fusobacterial RNA-binding protein involved in host small RNA-mediated growth inhibition

Host-derived small RNAs are emerging as critical regulators in the dynamic interactions between host tissues and the microbiome,with implications for microbial pathogenesis and host defense. Among these, transfer RNA-derived small RNAs (tsRNAs) havegarnered attention for their roles in modulating microbial behavior. However, the bacterial factors mediating tsRNA interaction andfunctionality remain poorly understood. In this study, using RNA affinity pull-down assay in combination with mass spectrometry,we identified a putative membrane-bound protein, annotated as P-type ATPase transporter (PtaT) in Fusobacterium nucleatum (Fn),which binds Fn-targeting tsRNAs in a sequence-specific manner. Through targeted mutagenesis and phenotypic characterization,we showed that in both the Fn type strain and a clinical tumor isolate, deletion of ptaT led to reduced tsRNA intake and enhancedresistance to tsRNA-induced growth inhibition. Global RNA sequencing and label-free Raman spectroscopy revealed the phenotypicdifferences between Fn wild type and PtaT-deficient mutant, highlighting the functional significance of PtaT in purine andpyrimidine metabolism.