E4orf4 sensitizes cells to killing by drugs inducing DNA damage or replication stress.

Clone 13 cells were induced with Dox for two hrs to stimulate E4orf4 expression (+E4orf4), or were left uninduced (-E4orf4), and were then treated with 4 μM HU or 2.5 ng/ml NCS for three hrs or left untreated (Control). Cell survival was measured by a clonogenic assay using various cell dilutions, without further Dox addition. The number of colonies was counted two weeks later, and relative survival was calculated separately for–E4orf4 and +E4orf4 samples by defining both control samples as 100%. E4orf4 itself decreased cell viability to 40% of control cells. Two independent experiments, each with triplicate samples were performed. Error bars represent pooled standard deviation and statistical significance was determined using a paired student t test. *: p<0.05.