Effect of CREB overexpression and CREBM1 on the LDH-A promoter. (A) Hypoxic induction of the transfected GH reporter, relative to α-globin control (α), was measured by RNase protection assay. Hypoxic induction was increased by cotransfection of a CREB expression plasmid and decreased by expression of a dominant negative protein, CREBM1. (B) To test whether hypoxia influences the phosphorylation of CREB, Western blot analyses were performed with nuclear extracts from HeLa cells incubated in normoxia (N), hypoxia (H), or 20 μM forskolin (F). Blots were probed with an anti-phospho-CREB antibody (UBI) or an anti-CREB antibody (25C10G; Santa Cruz).