Due to their small genomes and limited number of encoded proteins, viruses exploit host proteins for entry, replication, and transmission. Identification of such host proteins, also termed host dependency factors (HDFs), is particularly important for identifying therapeutic targets. Over recent years, many groups have successfully used genome-wide CRISPR/Cas9 as a screening strategy for HDFs in viral infections.
One example is provided by Marceau et al. (2017), who aimed to dissect the host factors associated with dengue and hepatitis C (HCV) infection (two viruses in family Flaviviridae). ELAVL1, an RNA-binding protein encoded by the ELAVL1 gene, was found to be a critical receptor for HCV entry, and a remarkable divergence in host dependency factors was demonstrated between the two flaviviridae.