Dexamethasone (Dex) stimulated expression of mouse TPO (mTPO) mRNA transcripts and mTPO protein in HeLa cells after infection with the AdGRE.mTPO vector. (A) Northern analyses of total RNA (10 μg/lane) isolated from HeLa cells infected with Ad vectors. Cells were infected with AdGRE.mTPO (5 or 25 moi), an Ad vector containing a chimeric corticosteroid inducible promoter controlling the expression of the mTPO cDNA (lanes 1 through 4). After 24 hours, the cells were incubated with dexamethasone (25 nmol/L; lanes 3 and 4) or without dexamethasone (lanes 1 and 2) for an additional 24 hours. The RNA was hybridized with a mTPO cDNA probe (top) or a GAPDH (bottom) probe. Lane 1, AdGRE.CAT (5 moi) alone; lane 2, AdGRE.CAT (25 moi) alone; lane 3, AdGRE.CAT (5 moi) + Dex; lane 4, AdGRE.CAT (25 moi) + Dex. (B) Western blot analysis of total protein (50 μg/lane) isolated from HeLa cells infected with Ad vectors. Cells were infected with either AdNull (25 moi, lanes 1 and 2), or AdGRE.mTPO (25 moi, lanes 3 and 4). After 24 hours, the cells were incubated with dexamethasone (25 nmol/L) (lanes 2 and 4) or without dexamethasone (lanes 1 and 3) for an additional 24 hours. Anti-mTPO serum was used to detect the 35-kD mTPO protein.