FIG. 4.

PK-A expression increases hypoxic inducibility of the LDH-A promoter. Cells were cotransfected with a test plasmid, encoding the LDH-A promoter and GH reporter gene, and a control plasmid, encoding the α-globin promoter (α) and gene. Transfected cells were incubated in parallel in normoxia (N) and hypoxia (H), and expression of GH and α-globin was analyzed by RNase protection assay. (A) Expression of wild-type (WT) PK-A increased hypoxic induction of the GH reporter, while expression of a functionally inactive PK-A mutant did not affect hypoxic induction. (B) Mutations in either site B (HIF-1) or site A (CRE) abrogated hypoxic induction, and mutation of site A blocked the effect of PK-A as well.