%0 Journal Article %A Wang, Jingfeng %A Peng, Yousong %A Zhao, Lili %A Cao, Mengmeng %A Hung, Tao %A Deng, Tao %T Influenza A virus utilizes a suboptimal Kozak sequence to fine-tune virus replication and host response %D 2015 %J Journal of General Virology, %V 96 %N 4 %P 756-766 %@ 1465-2099 %R https://doi.org/10.1099/vir.0.000030 %I Microbiology Society, %X The segment-specific non-coding regions (NCRs) of influenza A virus RNA genome play important roles in controlling viral RNA transcription, replication and genome packaging. In this report, we present, for the first time to our knowledge, a full view of the segment-specific NCRs of all influenza A viruses by bioinformatics analysis. Our systematic functional analysis revealed that the eight segment-specific NCRs identified could differentially regulate viral RNA synthesis and protein expression at both transcription and translation levels. Interestingly, a highly conserved suboptimal nucleotide at −3 position of the Kozak sequence, which downregulated protein expression at the translation level, was only present in the segment-specific NCR of PB1. By reverse genetics, we demonstrate that recombinant viruses with an optimized Kozak sequence at the −3 position in PB1 resulted in a significant multiple-cycle replication reduction that was independent of PB1-F2 expression. Our detailed dynamic analysis of virus infection revealed that the mutant virus displays slightly altered dynamics from the wild-type virus on both viral RNA synthesis and protein production. Furthermore, we demonstrated that the level of PB1 expression is involved in regulating type I IFN production. Together, these data reveal a novel strategy exploited by influenza A virus to fine-tune virus replication dynamics and host antiviral response through regulating PB1 protein expression. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.000030