The H5N1-NS1 protein affects the host cell cycle and apoptosis through interaction with the host lncRNA PIK3CD-AS2.

Long noncoding RNAs (lncRNAs) are involved in the host antiviral response, but how host lncRNAs interact with viral proteins remains unclear. The NS1 protein of avian influenza viruses can affect the interferon-dependent expression of several host lncRNAs, but the exact mechanism is unknown. To further investigate the molecular mechanism and functions of NS1 proteins and host lncRNAs, we performed RNA-immunoprecipitation sequencing assays on A549 cells transfected with the H5N1-NS1 gene. We identified multiple sets of host lncRNAs that interact with NS1. The results of the RNA pulldown assay indicated that PIK3CD-AS2 can directly interact with NS1 in vitro. Immunofluorescence confocal microscopy showed that these proteins were colocalized in the nucleus. Further studies revealed that PIK3CD-AS2 can also inhibit the transcription of NS1, which in turn affects the translation of the NS1 protein. PIK3CD-AS2 overexpression regulates NS1 protein-induced cell cycle arrest and initiates apoptosis. We hope this work will help elucidate the molecular mechanisms associated with NS1 proteins in the study of viral infections to promote the development of potential treatments for patients infected with avian influenza A viruses.