EXPRESSION OF GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE DURING DIFFERENTIATION OF HD3 CELLS

The chicken erythroblast cell line HD3, which is infected with a tempe rature-sensitive avian erythroleukemia virus, becomes committed to dif ferentiate to an erythrocyte upon temperature shift in the presence of inducers (hemin and butyric acid). The activity of glyceraldehyde-3-p hosphate 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 correspon ding mRNA level occurred. Twenty-four hours post-induction the glycera ldehyde-3-phosphate dehydrogenase message decreased and virtually disa ppeared within 48 h. Glyceraldehyde-3-phosphate dehydrogenase activity did not follow the mRNA level and increased within 48 h post-inductio n and then started to fall. The discrepancy between glyceraldehyde-3-p hosphate dehydrogenase activity and the mRNA level is likely due to a difference in GAD protein and mRNA half-lives. The results also sugges t that enzyme activity could be regulated by post-translational events . Chicken erythrocytes expressed reduced levels of glyceraldehyde-3-ph osphate dehydrogenase activity. Thus the low level of GAD found in chi cken erythrocytes is associated with a turn off of GAD gene expression upon induction of erythroid differentiation.