Elucidating genes sufficient for viral entry into cells through sequential genome-wide CRISPR activation screens.

A preeminent goal of virology is to discover cellular genes that mediate virus entry. Genome-wide loss-of-function screens can illuminate single genes necessary for virus entry, but are stymied by genetic redundancy. Here we report a genome-wide CRISPR activation screening strategy to discover single genes that are sufficient for viral entry into normally-uninfectable cells. Sequential rounds of viral infection vastly enhanced screening sensitivity. This sequential screening strategy was generalizable to two unrelated viruses-Ebola and rabies viruses-and could broadly accelerate the discovery of viral entry factors.