(D) HeLa-cells stably expressing the pC4-reporter were transfected with control siRNA (ctrl) or two independent siRNAs (#1 and #2) directed against BET1 (siRNA #1 is shown in figure EV 2B). 2d post-transfection the pC4-secretion assay was performed for 0 and 10 min post induction of secretion. Representative images are shown (upper panel ctrl and lower panel #2 siRNA, respectively. Scale bar: 20 µm. Right panels represent magnifications of dashed areas. 