Deletion analysis of the Ink4b promoter region with and without IFNβ. Fragments of the Ink4b promoter region were cloned into the reporter plasmid pGL3-Basic. M1 cells, transiently transfected with these constructs, were cultivated in the presence or absence of IFNβ and analyzed after 24 hours for luciferase activity. Shown are relative values normalized for Renilla luciferase activity. Error bars depict standard error.