Updated publication reference for PubMed record(s): 31649314. Human respiratory syncytial virus (RSV) is a globally prevalent negative-stranded RNA virus, which can cause life-threatening respiratory infections in young children, elderly people and immunocompromised patients. Its transcription termination factor M2-1 plays an essential role in viral transcription, but the mechanisms underpinning its function are still unclear. We investigated the cellular interactome of M2-1 using green fluorescent protein (GFP)-trap immunoprecipitation on RSV infected cells coupled with mass spectrometry analysis. We identified 137 potential cellular binding partners of M2-1, among which many proteins associated either with translation or mRNA metabolism, and particularly mRNA maturation and stabilization. Specific immunoprecipitation using the GFP-trap was used to confirm the ability of the polyA-binding protein cytoplasmic 1 (PABPC1), a candidate with a major role in both cellular translation and mRNA stabilization, to interact individually with M2-1. PABPC1 was also shown to colocalize with M2-1 from its accumulation in IBAGs to its liberation in the cytoplasm. These results strongly suggest a continued association of M2-1 with viral mRNA and mRNA metabolism factors from transcription to translation, and imply that M2-1 may have an additional role in the fate of viral mRNA downstream of transcription.