TPA-INDUCED ARREST OF ERYTHROID-DIFFERENTIATION IS COUPLED WITH DOWN-REGULATION OF GATA-1 AND UP-REGULATION OF GATA-2 IN AN ERYTHROID CELL-LINE SAM-1

GATA-1 protein is thought to be a positive regulator of erythroid diff erentiation. However, ectopic expression of a conditional GATA-2/estro gen receptor chimera was shown to inhibit erythroid differentiation in a hormone-dependent manner, suggesting the negative regulation of ery throid differentiation by GATA-2 protein. Accordingly, we reasoned tha t the quantitative balance of GATA-1 and GATA-2 protein might affect e rythroid differentiation. In this report, we performed specific and qu antitative measurements of GATA-1 and GATA-2 protein in a new erythroi d cell line, SAM-1, after treatment with 12-O-tetradecanoylphorbol 13- acetate (TPA). On the basis of these measurements, we show that TPA-in duced arrest of erythroid differentiation is coupled with the upregula tion of GATA-2 protein, as well as the downregulation of GATA-1 protei n. Our results suggest that it is the precise quantitative balance of GATA-1 and GATA-2 protein that regulates erythroid differentiation. (C ) 1996 by The American Society of Hematology.