Taken together, these experiments indicate that the acidic region C terminal to CR3, the (EP)6 repeat, named AR1, for auxiliary region 1, by Ström et al. (17), contributes to E1A activation of early promoters E2, E3, and E4 during viral infection of human respiratory epithelial cells through an interaction with p300 and most likely the closely related host protein CBP. This evidence concerns the gene EP300 and viral infectious disease.