Gadd45 and Gadd153 messenger RNA levels are increased during hypoxia and after exposure of cells to agents which elevate the levels of the glucose-regulated proteins

Abstract

We have investigated overlapping activation pathways for two families of stress genes that are expressed in cells exposed to hypoxia. The growth arrest and DNA damage (gadd) genes are induced by DNA damage and irradiation, and their expression is associated with growth arrest. The glucose-regulated proteins (GRPs) are induced by chemical agents that disrupt protein trafficking in the endoplasmic reticulum such as tunicamycin and A23187 and by hypoxia. Here, we demonstrate that the treatment of NIH-3T3 cells with chemical inducers of GRPs results in increased levels of gadd45 and gadd153 mRNA as well as GRP78 mRNA. In addition, hypoxia was also able to increase gadd45, gadd153, and GRP78 mRNA. Therefore the GRP and gadd genes can be activated by similar stimuli (e.g., hypoxia and chemical inducers). However, the mechanisms leading to increased levels of GRP78 and gadd gene mRNA are different and may involve distinct protein kinases. Increased expression of GRPs after treatment with chemical inducers is sensitive to cycloheximide and the protein kinase inhibitors genistein, 2-aminopurine, and H7, whereas the increase in gadd gene mRNA could be blocked by the protein kinase inhibitors H7 and 2-aminopurine but not by genistein or cycloheximide. GRP78 induction occurs by a pathway that requires protein synthesis and is sensitive to genistein, H7, and 2-aminopurine, whereas gadd gene induction is independent of protein synthesis and is inhibited by H7 and 2-aminopurine only.