SRSF3 facilitates replication of influenza A virus via binding and promoting the transport of viral mRNA.

Many host factors were involved in regulating the polymerase activity of influenza A virus. To fully explore the role of polymerase complex-related host factors, we combined high-throughput transcriptome data to analyze the changes in mRNA levels of these factors during viral infection. Transcriptome data showed that viral infection caused down-regulation of MYH9, HNRNPU, SRSF3 and RPS24 mRNA levels. We confirmed the changes in mRNA and protein levels of MYH9, HNRNPU and SRSF3 by qPCR and WB. Then their effects on virus replication were tested through overexpression and knockdown experiments. We emphatically explained the mechanism of SRSF3 during influenza virus replication. Results showed that SRSF3 promoted influenza virus replication and regulated viral protein expression at the post-transcriptional level. Further analysis found that SRSF3 regulated viral replication depends on the 88th amino acid. RIP and FISH experiments further proved that SRSF3 bound to viral mRNA and participated in the nuclear and cytoplasmic transport of viral mRNA. Collectively, these findings suggested that virus infection regulated the expression of many host factors and SRSF3 positively regulated virus replication.