NF-E2P18 MAFK IS REQUIRED IN DMSO-INDUCED DIFFERENTIATION OF FRIEND-ERYTHROLEUKEMIA CELLS BY ENHANCING NF-E2 ACTIVITY/

When Friend murine erythroleukemia (F-MEL) cells are induced to differ entiate by dimethylsulfoxide (DMSO), erythroid-specific genes are tran scriptionally activated. The erythroid transcription factor NF-E2 is e ssential for enhancer activity of the globin locus control regions. NF -E2 functions as a heterocomplex consisting of a 45-kDa subunit (NF-E2 p45) and a 18-kDa subunit (NF-E2p18). The larger subunit NF-E2p45 is t issue-restricted and is believed to play a role in globin gene express ion in F-MEL cells. The expression of the smaller subunit NF-E2p18, wh ich is a Maf family member (MafK), is cell type- and developmental sta ge-specific. We have investigated the possible role of NF-E2p18 in Fri end erythroid differentiation by stably transfecting either sense and antisense p18 constructs into differentiation-sensitive 745A and parti ally defective-differentiation TFP10 cell lines. Overexpression of NF- E2p18 induced expression of globin transcripts in both cell lines and increased their sensitivity to erythroid differentiation when exposed to DMSO. Conversely, inhibition of p18 expression by antisense transcr ipts resulted in the inhibition of DMSO-induced differentiation in bot h cell lines. These results indicate that NF-EPp18 is necessary for gl obin expression in F-MEL cells and that it is the predominant gene of the Maf family involved in DMSO-induced erythroid differentiation. Mor eover F-MEL clones overexpressing NF-E2p18 showed an increase in speci fic NF-ES DNA-binding activity whereas this activity was decreased in clones expressing antisense p18. Finally, studies using transient tran sfection assays showed that p18 activated NF-E2 site-dependent transcr iption in F-MEL cells. These data suggest that NF-E2p18 can participat e in DMSO-induced erythroid differentiation of F-MEL cells by enhancin g NF-E2 activity.