Evidence that Human parainfluenza virus type 2 paramyxovirus antigenomes are edited during infection

Mononegaviruses mRNA synthesis relies on cis-acting sequences for gene start and Gene end and non-templated nucleotide insertions at editing sites. Gene start and Gene end are silent during genome replication but editing site signals are actively utilized during antigenome synthesis. Amplicon sequencing of wildtype and NP mutants infection rPIV219 showed that antigenomes are edited at frequencies similar to mRNA with 2G insertions. Paramyxovirus replications always adheres to rule of six with genomes length being always multiples of 6 and because of this, edited genomes with 2 more insertions serve as poor replication templates. The NP-Q202A mutation helped relieve this constraint and tripled the accumulation of edited pre-geniomes intracellularly providing genetic evidence that antigenomes are indeed edited during infection. Despite the intracellular accumulation of non 6n+-o genomes, supernatant virions still selectively packaged only unedited 6n+0 genomes. This demonstrates that the rule of six is still kept true even by a combination of replication inhibition of non hexamer templates and exclusion at viral assembly and budding off. 
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