Identification of the functional domains of the matrix protein of influenza A/WSN/33 virus

Abstract

Background: The matrix protein (M1) of influenza virus plays a central role in viral replication and has been ascribed a variety of functions including association with viral RNA and ribonucleoprotein (RNP). It is essential to understand the binding mechanism by identification of the functional domains of M1. Methods: The RNA and RNP-binding domains of M1 protein were identified by introducing amino-acid substitutions and deletions. The RNA–protein interaction was investigated by measuring the binding of radiolabeled RNA to immobilized M1 protein. Reconstitution of M1 with RNP was studied by incubation of radiolabeled M1 with purified RNP. Results: We characterized RNA-binding domains of M1 protein by mutating M1, and show that M1 binds to RNA through two independent domains, a zinc-finger motif and a series of basic amino acids (RKLKR). One of the RNA-binding domains consisting of a series of basic amino acids is also involved in RNP binding. An independent domain located in the N-terminal 76 amino acids of M1 also participates in RNP-binding activity. Conclusions: The data suggest that M1 interacts with both the RNA and protein components of RNP in assembly/disassembly of influenza A viruses.