Hosta

English: Figure 3. Outline of the norovirus replication cycle. Human and murine noroviruses (turquoise hexagons) attach to the cell surface using carbohydrate attachment factors and cofactors (1). To mediate entry, binding to a protein receptor is required (2). After entry (3) and uncoating (4), the incoming viral genome is translated through interactions with genome-linked protein VPg (nonstructural protein NS5, red triangle) at the 5′ end of the genome and the cellular translation machinery (5). The open-reading frame 1 polyprotein is co- and post-translationally cleaved by the viral protease (NS6, blue flash) (6). The replication complex is formed by recruitment of cellular membranes to the perinuclear region of the cell, through interactions with NS1/2 (rose shape) and NS4 (yellow shape) (7). Genome replication occurs via a negative-strand intermediate (dashed line) (8), and genomic and subgenomic RNA (unbroken lines) are generated by the viral RNA-dependent RNA polymerase (NS7, green jagged circle), using de novo and VPg- or internal promoter-dependent mechanisms (9). Replicated genomes are translated or packaged into the capsid (in the case of whole-length genomes), composed mainly of viral protein 1 (VP1), for virion assembly (10) and exit (11).