Activity of MLL3 protein variants. Recombinant histone H3 protein was methylated with radioactively labeled AdoMet by MLL3-SET wild-type and MLL3-SET mutant proteins either alone or in the presence of complex member proteins. (A) Example of an autoradiographic image of the SDS polyacrylamide gel. The methylation signal of H3 is indicated. (B) Quantitative analysis of the averages of duplicate experiments. The error bars indicate the standard error of the mean.