Table S1.

Histone H4 (1-21) peptides

Peptide	Sequence	Expected mass, Da	Observed mass, Da*
H4 (1-21) WT	Ac-SGRGKGGKGLGKGGAKRHRKV	2,133	2,133
H4 (1-21) R17A	Ac-SGRGKGGKGLGKGGAKAHRKV	2,048	2,049
H4 (1-21) R17K	Ac-SGRGKGGKGLGKGGAKKHRKV	2,105	2,106
H4 (1-21) R17MMA	Ac-SGRGKGGKGLGKGGAKR(me)HRKV	2,147	2,148
H4 (1-21) R19A	Ac-SGRGKGGKGLGKGGAKRHAKV	2,048	2,049
H4 (1-21) R19K	Ac-SGRGKGGKGLGKGGAKRHKKV	2,105	2,106
H4 (1-21) R3K	Ac-SGKGKGGKGLGKGGAKRHRKV	2,105	2,106

^*Data from MALDI-TOF analysis show monoisotopic M+1 values; bold residues indicate the modified positions in each peptide.