# Coupling of polymerase-nucleoprotein-RNA in an influenza virus mini ribonucleoprotein complex

## TL;DR

Researchers used cryo-EM to determine the structure of influenza virus ribonucleoprotein complexes, revealing how their components interact and change during the virus's life cycle.

## Contribution

The study provides atomic-resolution cryo-EM structures of mini-vRNPs in two distinct conformations, revealing FluPol–NP–RNA coupling and conformational shifts.

## Key findings

- Cryo-EM structures show FluPol located inside or at the outer rim of the NP–RNA ring.
- NP-0 binds the RNA promoter and interacts with FluPol, with RNA strands occupying NP-0 grooves.
- State-In blocks FluPol interfaces, while State-Out exposes them, suggesting conformational changes during the viral life cycle.

## Abstract

Influenza virus ribonucleoprotein complexes (RNPs), composed of the polymerase complex (FluPol), nucleoprotein (NP), and RNA, are essential for replication and transcription. We report atomic-resolution cryo-EM structures of mini-vRNPs in two states: FluPol located inside (State-In) or at the outer rim (State-Out) of the NP–RNA ring. In both states, the 5′ and 3′ termini of vRNA are bound to FluPol as previously reported. One NP (NP-0) contacts PA/PB1 of FluPol and binds the distal double-stranded vRNA promoter, with its D72–K90 loop inserting into the RNA fork; separated strands occupy NP-0 RNA-binding grooves. Grooves from other NPs form a continuous RNA-protective path, consistent with negative-strand RNA virus mechanisms. In State-In, interfaces for FluPol dimerization or Pol II interaction are blocked, but fully exposed in State-Out. These structures reveal detailed FluPol–NP–RNA coupling and suggest a conformational shift in RNPs during the viral life cycle.

Influenza virus ribonucleoprotein complexes (RNPs) are essential for replication and transcription. Here, authors solve the cryo-EM structure of influenza mini-vRNP to reveal detailed FluPol–NP–RNA coupling and suggest a conformational shift in RNPs during the viral life cycle.