The C-Terminal 300 Amino Acid Residues of the G Protein and Putative Open Reading Frame X of the G Gene of Tailam Paramyxovirus (TlmPV) Are Not Required for Replication in Tissue Culture Cells

Tailam paramyxovirus (TlmPV) was identified in Sikkim Rats in Hong Kong, China in 2011. Its negative sense RNA genome is similar to J paramyxovirus (JPV) and Beilong paramyxovirus (BeiPV), the prototypes of the recently established genus Jeilongvirus. TlmPV genome is predicted to have eight genes in the order 39-N-P/V/C-M-F-SH-TM-G/X-L-59. The predicted size of the TlmPV G protein is 1,052 amino acid (aa) residues and much larger than G proteins of typical paramyxoviruses, which are often less than 800 aa. In addition to G open reading frame (ORF) in the G gene, another ORF, termed ORF-X exists in the G gene transcript. Similar ORF-X exists in JPV and BeiPV G gene, but their expression in virus-infected cells has not been confirmed. In this study, we generated infectious TlmPV using a newly developed reverse genetics system. We have found that the G protein of TlmPV is truncated in cultured cells: stop codons emerged in the G open reading frame, resulting in deletions of amino acid residues beyond residue 732. We have obtained infectious TlmPV lacking the C-terminal 307 aa (rTlmPV-G745) and TlmPV lacking the C-terminal 306 aa and the ORF-X (rTlmPV-GD746-X). The recombinant TlmPVs lacking the C-terminal 300 aa reach a higher peak viral titer and have improved genome stability in tissue cultured cells. The work indicates that the C-terminal of the G protein of TlmPV and ORF-X are not required for replication in tissue culture cells, and the deletion of the C-terminal confers a growth advantage in tissue culture cells. IMPORTANCE TlmPV is a member of the recently established genus Jeilongvirus. TlmPV encodes a large G protein and its G gene contains ORF-X. In this work, infectious TlmPV was recovered using reverse genetics. Using this system, we have demonstrated that 300 aa of C-terminal of G and the ORF-X are not required for viral replication in tissue culture cells.