TRANSCRIPTIONAL REGULATION OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE BY 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN

The action of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) on transcription and steady-state mRNA levels, protein expression, and enzymatic activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in cultured human keratinocytes was examined. GAPDH transcription increased as a function of time of exposure to TCDD, reaching a maximum of 23-fold after 8 days. Northern blot analysis showed a 4-fold increase in mRNA after 8 days exposure. Protein levels were increased 4-fold, and dehydrogenase activity by 5-fold, under the same exposure conditions. GAPDH is commonly thought of as a constitutive housekeeping gene and is often used as a loading control for northern blot analysis. Our data suggest that caution should be used when using GAPDH as an RNA control, especially in studies examining cell proliferation and carcinogenesis. (C) 1995 Academic Press, Inc.