Precise characterization of human histones in the H2A gene family by top down mass spectrometry.

Top Down analysis revealed that at least fourteen genes encoding histone H2A are coexpressed in HeLa cells. Characterization of these species revealed that all except H2A.Z and H2A.F/Z were alpha-N-acetylated, H2A.O and H2A.C,D,I,N,P were the most abundant, and those exceeding approximately 10% abundance lacked post-translational modifications. This unequivocal identification of H2A forms illustrates the advantages of Top Down Mass Spectrometry and provides a global perspective of H2A regulation through the cell cycle.