From the analyzed strains (Table S4) , we identified 42 essential yeast genes that, when dox-depleted, altered BMV-directed Rluc expression at least 6-fold in both passes at the same time point (Tables 1 and 2) . A more stringent 6-fold cutoff was used in the primary screen in response to our observation that some strains in this essential gene library showed more luciferase assay variability than in our previous screen of non-essential genes. This increased variability is likely due to the fact that these genes are essential for cell growth. Thus, upon dox-induced repression of these genes, the experiment is a race between specific effects of the relevant gene on virus replication and the nonspecific, general suppression of cell growth and viability that eventually occur with each strain. Therefore, the results are more subject to variations due to small changes in growth conditions or timing of the experiments. Accordingly, a 6-fold cutoff was employed to limit the inclusion of false positives.