Protein Arginine Methyltransferase 1 Interacts with and Activates p38α to Facilitate Erythroid Differentiation
Figure 6
PRMT1 stimulated EPO-induced erythroid differentiation in primary human CD34+ hematopoietic progenitor cells which required the activation of p38 MAPK.
(A) The PRMT1 methyltransferase activity in the homogenates of human CD34+ cells was assayed by in vitro methylation using hnRNP K (2 µg) as a substrate and visualized by fluorography. (B) Upon EPO treatment, PRMT1 activity was rapidly stimulated and reached its peak at 2 hr, as shown with three different substrates: hnRNP K, hnRNP A1 and hnRNP A2. A representative fluorograph from Donor A is shown. (C) The results from four individuals were expressed as fold stimulation at 2 hr after EPO treatment. Methyl incorporation into protein substrates was quantified by liquid scintillation counting. (D) PRMT1 protein levels did not change after EPO treatment. (E) The recombinant TAT-conjugated HA-PRMT1 proteins were introduced into CD34+ cells through the protein transduction method. HA-GFP recombinant proteins served as a negative control. (F, G) TAT-PRMT1 (0.1 µM) significantly stimulated the EPO-induced erythroid differentiation of CD34+ cells, as measured by benzidine staining and the surface expression of glycophorin A. Experiments were performed with cells from at least three different donors. Data are presented as means ± S.E. of at least three independent experiments; *, p<0.05; **, p<0.01; ***, p<0.005 compared with EPO-treated cells.
