title: A Nucleolar Protein, Ribosomal RNA Processing 1 Homolog B (RRP1B), Enhances the Recruitment of Cellular mRNA in Influenza Virus Transcription.
abstract: Influenza A virus (IAV) undergoes RNA transcription by a unique capped-mRNA-dependent transcription, which is carried out by the viral RNA-dependent RNA polymerase (RdRp), consisting of the viral PA, PB1, and PB2 proteins. However, how the viral RdRp utilizes cellular factors for virus transcription is not clear. Previously, we conducted a genome-wide pooled short hairpin RNA (shRNA) screen to identify host factors important for influenza A virus replication. Ribosomal RNA processing 1 homolog B (RRP1B) was identified as one of the candidates. RRP1B is a nucleolar protein involved in ribosomal biogenesis. Upon IAV infection, part of RRP1B was translocated from the nucleolus to the nucleoplasm, where viral RNA synthesis likely takes place. The depletion of RRP1B significantly reduced IAV mRNA transcription in a minireplicon assay and in virus-infected cells. Furthermore, we showed that RRP1B interacted with PB1 and PB2 of the RdRp and formed a coimmunoprecipitable complex with RdRp. The depletion of RRP1B reduced the amount of capped mRNA in the RdRp complex. Taken together, these findings indicate that RRP1B is a host factor essential for IAV transcription and provide a target for new antivirals.
  
  
  OBJECTIVE
  Influenza virus is an important human pathogen that causes significant morbidity and mortality and threatens the human population with epidemics and pandemics every year. Due to the high mutation rate of the virus, antiviral drugs targeting viral proteins might ultimately lose their effectiveness. An alternative strategy that explores the genetic stability of host factors indispensable for influenza virus replication would thus be desirable. Here, we characterized the rRNA processing 1 homolog B (RRP1B) protein as an important cellular factor for influenza A virus transcription. We showed that silencing RRP1B hampered viral RNA-dependent RNA polymerase (RdRp) activity, which is responsible for virus transcription and replication. Furthermore, we reported that RRP1B is crucial for RdRp binding to cellular capped mRNA, which is a critical step of virus transcription. Our study not only provides a deeper understanding of influenza virus-host interplay, but also suggests a potential target for antiviral drug development.
authors: Research Center for Emerging Viruses, China Medical University Hospital, Taichung, Taiwan China Medical University, Taichung, Taiwan.
authors: Wen-Chi
authors: WC
authors: Su
authors: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
authors: Shih-Feng
authors: SF
authors: Hsu
authors: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
authors: Yi-Yuan
authors: YY
authors: Lee
authors: Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan National RNAi Core Facility, Academia Sinica, Taipei, Taiwan.
authors: King-Song
authors: KS
authors: Jeng
authors: Research Center for Emerging Viruses, China Medical University Hospital, Taichung, Taiwan China Medical University, Taichung, Taiwan Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan michlai@gate.sinica.edu.tw.
authors: Michael M C
authors: MM
authors: Lai
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000502:physiology*; D004285:Dogs; D057809:HEK293 Cells; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics*; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics*; D007763:Lac Operon / Q000235:genetics; D061985:Madin Darby Canine Kidney Cells; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics*; D034741:RNA, Small Interfering; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics*; D014779:Virus Replication / Q000235:genetics
chemical_list: D051017:Apoptosis Regulatory Proteins; D002868:Chromosomal Proteins, Non-Histone; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D012367:RNA, Viral; C574722:RRP1B protein, human; D012324:RNA-Dependent RNA Polymerase