Transcriptional activity is essential for HIF-1α induction by LPS. NR8383 cells were pretreated or not for 15 minutes with actinomycin D (100 ng/mL) and maintained under control conditions, in the presence of 1 μg/mL LPS (A) or under hypoxic conditions (B) for 6 hours. Total cell extracts (25 μg) were resolved by SDS-PAGE (8% gel) and immunoblotted using an anti-HIF-1α antiserum or an antiphospho-p44/p42 MAPK monoclonal antibody.