Ultrastructural analysis of the virus ribonucleoprotein complexes by high-speed atomic force microsccopy

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K08808
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Virology
• Research Institution: Kyoto University
• Principal Investigator: Nakano Masahiro 京都大学, ウイルス・再生医科学研究所, 助教 (90456997)
• Research Collaborator: KODERA NORIYUKI
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: インフルエンザウイルス / 転写 / 複製 / 原子間力顕微鏡

Outline of Final Research Achievements

The influenza viruses have segmented single-stranded negative-sense RNAs (vRNAs) as their genomes. Each vRNA segment is encapsidated by viral nucleoproteins and an RNA-dependent RNA polymerase to form a ribonucleoprotein complex (vRNP) with a rod-shaped, double-helical structure. The vRNA is either transcribed into mRNA or replicated into complementary RNA (cRNA) in context of the vRNP. However, the vRNP conformation during transcription and replication remains unknown. Here, we employed high-speed atomic force microscopy to visualize native structure of vRNPs producing viral RNA in vitro. Our analysis showed two types of vRNPs that are associated with newly synthesized RNAs; 1) intact rod-shaped helical vRNP connecting with a structured RNA and 2) deformed vRNP associated with a looped double-stranded RNA. Our findings provide important insights into viral RNA synthesis by influenza virus vRNPs and suggest mechanisms for transcription and replication of the influenza virus genome.

Free Research Field

ウイルス学

Academic Significance and Societal Importance of the Research Achievements

RNA合成中のリボヌクレオタンパク質複合体（vRNP）の構造については、インフルエンザウイルスのみならずその他のウイルスでも報告がなく、本課題において初めてその微細構造を明らかにできたという点で学術的意義は大きい。また、インフルエンザウイルスは感染細胞内では二本鎖RNAを作らないと従来考えられてきたが、本成果によりvRNPがin vitroにおいて二本鎖RNAを合成することが明らかとなった。ウイルスの二本鎖RNAは宿主の自然免疫応答を引き起こすことから、感染細胞内でも二本鎖RNAを形成させるような条件を今後確立できれば、新たな治療薬の開発へとつながりその社会的意義も大きいと考える。