6i54 | pdb_00006i54
Influenza A nucleoprotein docked into 3D helical structure of the wild type ribonucleoprotein complex obtained using cryoEM. Conformation 2.
Structural highlights
Function[Q1K9H2_I33A0] Encapsidates the negative strand viral RNA, protecting it from nucleases. The encapsidated genomic RNA is termed the ribonucleoprotein (RNP) and serves as template for transcription and replication. The RNP needs to be localized in the nucleus to start an infectious cycle, but is too large to diffuse through the nuclear pore complex. NP comprises at least 2 nuclear localization signals and is responsible of the active RNP import into the nucleus through the cellular importin alpha/beta pathway. Later in the infection, nucleus export of RNP are mediated through viral proteins NEP interacting with M1 which binds nucleoproteins. It is possible that the nucleoprotein binds directly exportin-1 (XPO1) and plays an active role in RNP nuclear export. M1 interaction with RNP seems to hide nucleoprotein's nuclear localization signals. Soon after a virion infects a new cell, M1 dissociates from the RNP under acidification of the virion driven by M2 protein. Dissociation of M1 from RNP unmask nucleoprotein's nuclear localization signals, targeting the RNP to the nucleus (By similarity).[SAAS:SAAS002141_004_603280] Publication Abstract from PubMedThe influenza virus genome consists of eight viral ribonucleoproteins (vRNPs), each consisting of a copy of the polymerase, one of the genomic RNA segments and multiple copies of the nucleoprotein arranged in a double helical conformation. vRNPs are macromolecular machines responsible for messenger RNA synthesis and genome replication, that is, the formation of progeny vRNPs. Here, we describe the structural basis of the transcription process. The mechanism, which we call the 'processive helical track', is based on the extreme flexibility of the helical part of the vRNP that permits a sliding movement between both antiparallel nucleoprotein-RNA strands, thereby allowing the polymerase to move over the genome while bound to both RNA ends. Accordingly, we demonstrate that blocking this movement leads to inhibition of vRNP transcriptional activity. This mechanism also reveals a critical role of the nucleoprotein in maintaining the double helical structure throughout the copying process to make the RNA template accessible to the polymerase. Structural insights into influenza A virus ribonucleoproteins reveal a processive helical track as transcription mechanism.,Coloma R, Arranz R, de la Rosa-Trevin JM, Sorzano COS, Munier S, Carlero D, Naffakh N, Ortin J, Martin-Benito J Nat Microbiol. 2020 Mar 9. pii: 10.1038/s41564-020-0675-3. doi:, 10.1038/s41564-020-0675-3. PMID:32152587[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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