147 ISSN 1746-0794 Future Virology (2014) 9(2), 147–160 REVIEW Background Caliciviruses are a diverse family comprising animal and human viruses that are ubiquitous in the environment. The Caliciviridae family contains five genera: Norovirus, Sapovirus, Lagovirus, Vesivirus and Beco/Nebovirus ; and three proposed genera, Recovirus, Valovirus and Bavovirus [1–3] . Norovirus, Sapovirus and Recovirus cause gastroenteritis in humans [4] and can also infect a number of animals. However, Lagoviruses, Vesiviruses and Beco/Neboviruses primarily infect animals and cause a variety of diseases. Noroviruses in particular are considered the leading cause of outbreaks and sporadic cases of viral gastroenteritis worldwide [5] . Caliciviruses are small icosahedral nonenveloped particles of 27–40 nm in diameter that have a positive-sense ssRNA genome of approximately 7.6–8.6 kb in length. In addition, these viruses produce a subgenomic (sg) RNA, which is produced during infection, and is identical to the 3´ end of the genome (Figure 1) . Both RNAs are polyadenylated, but lack the cap structure (m7GpppN) and contain a viral protein associated with the genome (VPg) [6,7] , which is covalently linked to the 5´ end. Genomic organization The RNA genomes of the caliciviruses share similar organization; they are divided into two up to four open reading frames (ORF), depending on the genus they belong to (Figure 1) [8–11] . ORF1, located towards the 5´ end of the genome, encodes for a polyprotein cotranslationally processed by a viral protease as nonstructural precursors, resulting in at least 6 nonstructural (NS) proteins, designated NS1 through NS7 [8,12,13] . In the case of the murine norovirus (MNV) infection, all NS proteins colocalize with dsRNA within the replication complex during the course of infec- tion [14] . The function of some of these proteins has been established: NS3 is an NTPase; NS5 is a viral protein associated with the genome VPg, which is involved in the initiation of translation [15–18] and genome replication [6,19] ; NS6 is the only protease described, which is responsible for the autocatalytic processing of the ORF1 polyprotein [11] ; and NS7 is an RNA-dependent RNA part of 10.2217/FVL.13.125 © 2014 Future Medicine Ltd REVIEW Host-cell factors involved in the calicivirus replicative cycle Ana Lorena Gutiérrez-Escolano* *Department of Infectomics & Molecular Pathogenesis, Center for Research & Advanced Studies (CINVESTAV), Mexico City, Mexico ABSTRACT: The Caliciviridae includes small positive-sense, ssRNA viruses, which infect both animals and humans and cause a wide range of diseases. Human caliciviruses are considered the leading cause of outbreaks and sporadic cases of viral gastroenteritis worldwide. Caliciviruses are nonenveloped with a positive-sense, ssRNA genome. As with other positive-sense, ssRNA viruses, they require interactions between viral components and host-cellular factors at diferent steps along the viral life cycle. Although knowledge about the role of host-cell proteins in the Caliciviridae life cycle remains modest, evidence on this topic is rapidly emerging. This article compiles and discusses the information regarding the involvement of host-cellular factors in the various stages of the calicivirus replication process, emphasizing factors that might be involved in viral translation and/or RNA replication. KEYWORDS • caliciviruses • canonical factors • host–cell interactions • noncanonical factors • RNA viruses • translation For reprint orders, please contact: reprints@futuremedicine.com