Here we report an unbiased genome-wide miRNA mimic-inhibitor screen (∼1000 miRNA in miRBase Sequence

13.0) to identify cellular miRNAs involved in productive HCV infection. In the primary screen applying an infectious HCVcc system, we identified 77 miRNAs that either enhanced (proviral) or restricted (antiviral) HCV infection.23 host proviral miRNAs and 41 host antiviral miRNAs were subsequently validated by a secondary screen using a luciferase reporter virus. Taking advantage of functional genomics and various in vitro HCV models, we investigated the functions of these host miRNAs see more in different stages of HCV life cycle – entry, trafficking, IRES-mediated translation, RNA replication, and assembly/secretion. We further characterized several representative miRNAs for their mechanisms in modulating

HCV infection. Multiple members of the let-7 family of miRNAs with conserved seed sequence were PD0325901 purchase shown to restrict HCV infection at multiple stages of viral life cycle. We performed target prediction by bioinformatics and various validation assays, and demonstrated that these let-7 miRNAs target and down-regulate various host proviral factors identified in our previous small interference RNA (siRNA) screen (Li et al, PNAS 2009) at either transcriptional or translational level, potentially

explaining the antiviral function of these miRNAs in HCV infection. A comprehensive investigation of cellular miRNAs modulating the complete HCV life cycle will yield critical insights into HCV pathogenesis and provide novel therapeutic targets. Disclosures: The following people have nothing to disclose: Qisheng Li, Siddharth Krishnamurthy, Helen Cha, Ramy El-Diwany, Stephan Chiu, Hawwa F. Alao, T. Jake Liang Background: Treatment of chronic viral infection is challenged by variability of viral targets and development of resistance. Viruses depend on host factors for their life cycle, selleck chemicals which are attractive alternative antiviral targets, provided that they are not mandatory for normal cell functions. Using a functional proteomic screen, we recently identified Receptor for Activated C Kinase 1 (RACK1) as a specific host factor required for replication of internal ribosome entry site (IRES)-containing viruses. Methods: Using state-of-the-art cell culture models for HCV infection, replication and translation, we investigated the functional impact of RACK1 as a host factor for HCV infection. Results: Silencing of RACK1 expression in Huh 7.5.1 cells resulted in a marked, specific and significant decrease in HCV Jc1 infection and infectious virion production.