The genome contains 8 transcription units with at least 9 open reading frames (ORFs) that encode a nucleocapsid protein (N), a matrix protein (M), a phosphoprotein (P) that likely associates with the polymerase complex, a fusion glycoprotein (F), an attachment glycoprotein (G), a large polymerase protein (L), a small hydrophobic protein (SH), and two proteins (M2-1 and M2-2) encoded by overlapping ORFs in the M2 gene. Among paramyxoviruses, SH is found in rubulaviruses and pneumoviruses, while M2 is found only in pneumoviruses. The functions of M2 proteins have not been studied extensively.