... by the DNA-nicking and DNA-attaching activities of NS1. Upon testing this hypothesis, we found that NS1 covalently binds to cellular DNA and is modified by PARP, an enzyme involved in repairing ... University of Jyväskylä, Jyväskylä, Finland 5. Division of Rheumatology, Department of Medicine, Pennsylvania State University College of Medicine/Milton S. Hershey Medical Center, Hershey, PA, USA ... induc-tion of protein expression. Caffeine was maintained on the cells during expression of GFP or GFP/NS1. PARP was inhibited by incubating transfected cells with 5-aminoisoquinolinone (Calbiochem)...