The SARS Coronavirus E Protein Interacts with PALS1 and Alters Tight Junction Formation and Epithelial Morphogenesis

Teoh, Kim-Tat; Siu, Yu-Lam; Chan, Wing-Lim; Schlüter, Marc A.; Liu, Chia-Jen; Peiris, J. S. Malik; Bruzzone, Roberto; Margolis, Benjamin; Nal, Béatrice

We applied a yeast-two-hybrid screening strategy to identify cellular proteins that could interact with the CT domain of E (Figure 1A) and screened a random-primed cDNA library from human placenta. Sequencing of positive cDNA clones (146 of 70 million interactions tested) revealed that 19% (28/146 clones) corresponded to human PALS1 cDNA fragments (accession number: NM_022474.2) (Figure 1B). The interaction between PALS1 and the CT domain of SARS-E protein was classified with high confidence score (Predicted Biological Score, PBS = A). Among the 28 PALS1 cDNA clones isolated from the screening, #67 and #131 constituted the smallest and largest PALS1 cDNA fragments, respectively. Clone 67 corresponded to its PDZ domain (amino acids 234-362) flanked by 20 and 25 amino acids at the upstream and downstream regions (Figure 1B, panel a), whereas clone 131 was a shorter form of PALS1 with truncations at both N- and C-terminal ends (amino acids 95-514, including domains L27, PDZ, SH3, band 4.1, and a truncated GuK) (Figure 1B, panel b). The yeast-two-hybrid screen thus indicated that E CT interacts with human PALS1 protein in yeast and that the minimal interacting fragment only consists of the PALS1 PDZ domain.