PRMT1 is critical for erythroid differentiation and β^maj-globin transcription. (A) Western blotting of MEL cells stably transduced with pSuper vector or PRMT1 shRNA was performed with the indicated antibodies. (B) Stable MEL clones harboring control or shPRMT1-expressing constructs were incubated with 1.5% DMSO and total RNA was extracted at days 0, 3, and 5. The β^maj-globin primary transcripts were analyzed by quantitative reverse-transcription (RT)–qPCR and normalized to β-actin. (C) MEL cell clones stably transduced with retrovirus encoded pSuper vector or PRMT1 shRNA (shPRMT1) were treated with 1.5% DMSO and hemoglobinization was assayed by benzidine staining at day 5. (D) PRMT1 expression of stable ES cell clones transduced with the control or shPRMT1 retroviral vectors was analyzed by Western blot analysis. (E) Stable ES cell clones transduced with the control or shPRMT1 retroviral vectors were treated with 2 U/mL EPO for 9 and 11 days and total RNA was isolated. β^maj-globin mRNA expression was analyzed by qRT-PCR and normalized using β-actin as a control. (F) ChIP analysis of USF1 and PRMT1 binding to HS2 and the β^maj-promoter in the parental and PRMT1 KD ES cells. (G) Analysis of the binding of GATA-1 to the mouse β-globin locus in control and PRMT1 KD cells. ChIP assay was carried out using antibodies specific to GATA-1 comparing pSuper vector control-transfected cells with the PRMT1 KD MEL cells. Precipitated DNA fragments were amplified by real-time quantitative PCR using primers specific to the HS2 core and the β^maj-promoter. Significant difference by Student t test: *P < .05, **P < .01. Shown are the mean ± SDM of 3 independent ChIP experiments.