Nuclear PLCbeta(1) acts as a negative regulator of p45/NF-E2 expression levels in Friend erythroleukemia cells.

It is well established that phospholipase C (PLC) beta(1) plays a role in the nuclear compartment and is involved in the signalling pathway that controls the switching of the erythroleukemia cells programming from an undifferentiated to a differentiated state. Constitutive overexpression of nuclear PLCbeta(1) has been previously shown to inhibit Friend cells differentiation. For further characterization, we investigated the localization of PLCbeta(1)a and PLCbeta(1)b in Friend cells by fusing their cDNA to enhanced green fluorescent protein (GFP). To investigate the potential target of nuclear PLCbeta(1) in Friend differentiation, we studied the expression of p45/NF-E2 transcription factor, which is an enhancer binding protein for expression of the beta-globin gene and the expression of GATA proteins that are important for the survival and differentiation of erythroid cells. Our data suggest that the overexpression of PLCbeta(1) (both 1a and 1b) only in the nuclear compartment significantly reduces the expression of p45/NF-E2. The effect observed is attributable to the specific action of nuclear PLCbeta(1) signalling given that GATA-1 and GATA-3 are not affected at all. Here we show the existence of a unique target, i.e. the transcription factor p45/NF-E2, whose expression is specifically inhibited by the nuclear signalling evoked by PLCbeta(1) forms.