Fuzziness in the core of the human pathogenic viruses HCV and HIV

Nucleocapsid proteins are the molecular jacks-of-all-trades of small RNA viruses because they play pivotal roles in viral genomic RNA selection and packaging, regulate genome replication and virus budding and at the same time orchestrate a complex, dynamic interaction network with host cell proteins contributing to viral persistence and pathogenecity. These promiscuous interactions are made possible by the intrinsic flexibility of viral nucleocapsid proteins, facilitating either simultaneous or sequential binding to a plethora of structurally unrelated substrates, resulting in flexible, ever-changing multiprotein, RNA-protein and lipid-protein complexes during the viral replicative cycle. In this chapter, we examine the flexibility and multifunctionality of the assemblages formed by the nucleocapsid proteins of two important human pathogens, hepatitis C virus and human immunodeficiency virus.