The HIRA-SAHF pathway is not induced by activated GSK3βS9A in MEFs. (a) Localization of HIRA and PML in control virus and H-RasG12V-transduced senescent IMR90 cells was examined by immunofluorescence. (b) MEFs examined as in (a). (c) DAPI-staining of representative cells from (a) and (b). (d) Expression of transduced constructs was verified by western blotting V5-tagged GSK3βS9A or Ras.