Increased expression of the distal, but not of the proximal, Gata1 transcripts during differentiation of primary erythroid cells

Gata1 is expressed from either one of two alternative promoters, the erythr oid (proximal to the AUG) and the testis (distal to the AUG) promoter, both used by hemopoietic cells. To clarify the role of the distal and proximal Gata1 transcripts in erythroid differentiation, Lye determined by specific reverse transcriptase-polymerase chain reactions their relative levels of e xpression during the differentiation of erythroid precursors purified from the spleen of mice treated with phenylhydrazine (PHZ) or infected with the anemia-inducing strain of the Friend virus (FVA cells). PHZ cells are eryth roid precursors that progress in vivo to erythroblasts in 3 days. Both PHZ and FVA cells synchronously proliferate and differentiate in vitro in the p resence of erythropoietin (EPO). The levels of total and of distal, but not of proximal, Gata1 transcripts increased by five- to eightfold during in v ivo and in vitro differentiation of FVA and PHZ cells. The increase in expr ession was temporally associated with an increase in the expression of Eklf , Scl, and Nfe2, three genes required for erythroid differentiation, and pr eceded by 24 h the repression of Gata2 and Myb expression. The day 1 PHZ ce lls that survived 18 h in the absence of EPO do not express globin genes an d express detectable levels of distal but not of proximal Gata1 transcripts . These cells activate the expression of the globin genes within 2 h when e xposed to EPO. Therefore, during erythroid differentiation of primary cells , increased expression of distal Gala I transcripts underlies the increase in the expression of total Gata1 associated with the establishment of the e rythroid differentiation program. (C) 1999 Wiley-Lisa Inc.