Effects of UPR mutants on DENV-2 virus production. Congenic MEF cells deficient in PKR (A), PERK (B), IRE1α (C), XBP1 (D), and ATF6α (E) were infected for the indicated times, and viral production was measured by plaque assay as previously described (see “Experimental Procedures”). Error bars indicate mean ± S.D.; n = 3.