If multiple post-translational modifications are responsible for important biological markers, additional specificity must be present to serve as embedded combinatorial markers for phosphorylation. In this investigation, we have attempted to elucidate the specificity of AURKB and Haspin by using peptides of various lengths that contain all possible methylations, acetylations, and phosphorylations in histone H3 N-terminal peptides. The activity of AURKB is affected by a wide range of modifications from R2 to K14, while that of Haspin is affected significantly by modifications at R2 and K4. In cases where kinase activity is reduced substantially by other modifications, dimethylation at R2 and R8 totally abolishes phosphorylation at S10 promoted by AURKB and as does dimethylation at R2 on Haspin promoted phosphorylation at T3.
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