m(6)A Modified Short RNA Fragments Inhibit Cytoplasmic TLS/FUS Aggregation Induced by Hyperosmotic Stress

Translocated in LipoSarcoma/Fused in Sarcoma (TLS/FUS) is a nuclear RNA binding protein whose mutations cause amyotrophic lateral sclerosis. TLS/FUS undergoes LLPS and forms membraneless particles with other proteins and nucleic acids. Interaction with RNA alters conformation of TLS/FUS, which affects binding with proteins, but the effect of m(6)A RNA modification on the TLS/FUS–RNA interaction remains elusive. Here, we investigated the binding specificity of TLS/FUS to m(6)A RNA fragments by RNA pull down assay, and elucidated that both wild type and ALS-related TLS/FUS mutants strongly bound to m(6)A modified RNAs. TLS/FUS formed cytoplasmic foci by treating hyperosmotic stress, but the cells transfected with m(6)A-modified RNAs had a smaller number of foci. Moreover, m(6)A-modified RNA transfection resulted in the cells obtaining higher resistance to the stress. In summary, we propose TLS/FUS as a novel candidate of m(6)A recognition protein, and m(6)A-modified RNA fragments diffuse cytoplasmic TLS/FUS foci and thereby enhance cell viability.