Protein arginine methyltransferase (PRMT)1, 5 and 6 can methylate recombinant and endogenous H2A. (A) Histone methyltransferase (HMT) assays with different Flag-hemagglutinin (HA)-tagged PRMTs immunoprecipitated from HEK 293, stably expressing PRMTs on (lane 1) nucleosomes, (lane 2) purified histones and (lane 3) recombinant full-length H2A. (Left) Coomassie stain and (right) autoradiography are shown. (B) HMT assays using recombinant full-length H2A and H2A 4-129. Only PRMT1 and 6 were found to methylate H2A 4-129. (C) HMT assays (left panel) with Flag-Ha-PRMT1 on H2A 4-129, H2A 4-129 R11 mutated to K, and (right panel) with Flag-Ha-PRMT6 on H2A 4-129, H2A 4-129 R11K, H2AR11K R29K. Loading controls are shown below. (D) Mass spectrometry (MS) analysis of H2 Amethylated in vitro by PRMT1 shows methylation of R11. Tandem MS (MS/MS) spectra of a propionylated histone H2A peptide at a mass:charge ratio (m/z) of 876 from trypsin digest of propionylated H2A is shown. (E) MS analysis of H2A, in vitro methylated by PRMT6 shows methylation of R29. MS/MS spectrum of a doubly-charged peptide ion at m/z of 703.901 is shown.