Mediates the regulatory switch from transcription to RNA replication (PubMed:10500164) (Probable). Acts late in infection by inhibiting viral transcription and up-regulating RNA replication (PubMed:16254330, PubMed:26474524). Inhibition of transcription by protein M2-2 requires phosphorylation of the phosphoprotein (PubMed:26474524). Belongs to the orthopneumovirus M2-2 protein family.