Fig. 9. E4-ORF1 functionally disrupts TJs in MDCK cells. (A) Prevention or delay of TER establishment in MDCK-E4-ORF1 and MDCK-E4-ORF1-low monolayers, respectively. The arrow indicates the time when TER values became stabilized (72 hours post-plating). CREF fibroblasts were used as a negative control in the assay. (B) Comparable E4-ORF1 expression by MDCK-E4-ORF1 cells and MDCK-IIB cells. Extracts (150 µg protein) of the indicated sample buffer-lysed cells were immunoblotted with E4-ORF1 or Erk1/2 antibodies. Erk1/2 served as a loading control. (C) Prevention of TER establishment in MDCK-IIB monolayers. TER values were determined for fully confluent cells on Transwell filters at the indicated times post-plating.