The m6A reader protein YTHDF2 facilitates HTLV-1 infectious and mitotic propagation by stabilizing Tax RNA.

N6-methyladenosine (m6A) is one of the important RNA modifications that affect RNA abundance and function and has also been implicated in viral infection. In this study, we identified a number of m6A modification sites within human T-cell leukemia virus type 1 (HTLV-1) RNAs, particularly in the RNA of the Tax oncogene. We demonstrated that YTH domain family member 2 (YTHDF2), a key m6A reader protein that binds m6A-modified RNAs and influences RNA metabolism, is required for HTLV-1 replication in both de novo and persistently infected cells. Mechanistically, YTHDF2 interacts with and stabilizes Tax RNA in an m6A-dependent manner, thereby promoting Tax-driven HTLV-1 replication. Importantly, YTHDF2 activates oncogenic cellular pathways and promotes proliferation in HTLV-1-infected cells, aligning with the functions of Tax. Overall, our findings characterize YTHDF2 as a host factor critical to HTLV-1 RNA metabolism and viral propagation, offering novel insights into the understanding of the HTLV-1 life cycle and the development of targeted interventions.IMPORTANCEm6A is an RNA modification that plays crucial roles in physiological and pathological conditions; however, its roles in HTLV-1 infection are poorly understood. In this study, we identified that m6A modification is widely present in HTLV-1 RNAs, including Tax. We demonstrate that YTHDF2, a prominent m6A reader protein, enhances the stability of Tax RNA, thereby promoting both de novo and persistent HTLV-1 replication. Our findings position YTHDF2 as an essential factor for HTLV-1 persistence and suggest it as a potential therapeutic target for viral clearance.