 These results will be extended to virus infection assays. G1 specific cells isolated by drug treatment will be infected with Ad vectors expressing epitope tagged proteins as appropriate. Association of E1A and HBO1 and their mutant derivatives will be determined. This assay will allow us to confirm the effect of E1A stimulated HAT activity in origin firing and study the effects of E1A on origin firing, if any, other than increasing the HAT activity of HBO1. 