We also looked for insertions outside of the region that encoded the non-essential genes M2-1 and SH. RT-PCR was performed on rhMPV/ΔM2-2 and rhMPV total RNA to amplify the N/P, P/M, F/M2, SH/G and G/L non-coding sequences. There was a total of 23 poly A tracts and 2 poly U tracts with 4 or more contiguous A or U residues, respectively, among these sequences. However, no insertions of A were observed in the any of these non-coding sequences, showing that the high frequency of A insertions was predominantly confined to the region encoding the non-essential genes M2-1 and SH.