Table 2. Mass spectrometric analysis of the total acetylation levels on H3K9, H3K14, H3K18, H3K23 and H3K27 in adenoviral GFP‐ or Cre‐infected CBPflox/flox;p300flox/flox MEFs
PeptideMH+ΔM (p.p.m.)Peak area ( × 106)Ratio (GFP/Cre)
GFPCre
9KSTGG14KacAPR943.53201.521324.51264.11.05
9Kme1STGG14KacAPR957.54760.37277.4340.20.82
9Kme2STGG14KacAPR971.56330.141389.31414.40.98
9KacSTGG14KacAPR985.54250.1361.554.31.13
Sum of 14Kac3052.73072.90.99
18KQLAT23KacAAR1028.62110.874239.55058.20.84
18Kme1QLAT23KacAAR1042.63681.1927.248.20.56
18KacQLAT23KacAAR1070.63170.891036.936.728.29
Sum of 23Kac5303.65143.11.03
27KacSAPATGGV36Kme2KPHR1503.87540.2420.21.315.23
  • The histone H3 proteins isolated from MEFs were digested with endoproteinase Arg‐C to release three peptides: the 9KSTGG14KAPR encompassing residues K9–R17, the 18KQLAT23KAAR encompassing K18–R26, and the 27KSAPATGGV36KKPHR encompassing K27–R40. The peak area value represents the abundance of each type of modified peptides determined by mass spectrometry, with the relative standard deviation of ∼15%. Note that K9ac was always detected with co‐existing K14ac on the same peptide to form 9KacSTGG14KacAPR (H3K9/14ac), that K18ac was always detected with co‐existing K23ac on the same peptide to form 18KacQLAT23KacAAR, that K27ac was always detected with co‐existing K36me2 on the same peptide to form 27KacSAPATGGV36Kme2KPHR, and that K36ac and K56ac were undetectable.