Expression of glyceraldehyde-3-phosphate dehydrogenase during differentiation of HD3 cells

The chicken erythroblast cell line HD3, which is infected with a temperature-sensitive avian erythroleukemia virus, becomes committed to differentiate to an erythrocyte upon temperature shift in the presence of inducers (hemin and butyric acid). The activity of glyceraldehyde-3-phosphate dehydrogenase (GAD), a key enzyme in the glycolytic pathway, was examined. Upon induction of differentiation the following changes in glyceraldehyde-3-phosphate dehydrogenase activity and the corresponding mRNA level occurred. Twenty-four hours post-induction the glyceraldehyde-3-phosphate dehydrogenase message decreased and virtually disappeared within 48 h. Glyceraldehyde-3-phosphate dehydrogenase activity did not follow the mRNA level and increased within 48 h post-induction and then started to fall. The discrepancy between glyceraldehyde-3-phosphate dehydrogenase activity and the mRNA level is likely due to a difference in GAD protein and mRNA half-lives. The results also suggest that enzyme activity could be regulated by post-translational events. Chicken erythrocytes expressed reduced levels of glyceraldehyde-3-phosphate dehydrogenase activity. Thus the low level of GAD found in chicken erythrocytes is associated with a turn off of GAD gene expression upon induction of erythroid differentiation.