Quantitative mass spectrometry analysis of modifications on histone H3 of HPV1 virions and primary HFK control cells. (A) Relative abundance of H3 histone acetylation and methylation as a percentage of total modified and unmodified peptides (H3 peptides TKQTAR, aa 3 to 8; KSTGGKAPR, aa 9 to 17; KQLATKAAR, aa 18 to 26; KSAPATGGVKKPHR, H3.1 aa 27 to 40; KSAPSTGGVKKPHR, H3.3 aa 27 to 40) in histones extracted from HPV1 virions (HPV), proliferating human foreskin keratinocytes (growing), partially differentiated human foreskin keratinocytes (Ca++), or fully differentiated human foreskin keratinocytes grown as organotypic skin equivalents (raft). n = 2, HPV1; n = 6, cell samples. Error = SD. (B) The proportion of modification of each residue was calculated for HPV1 (average, n = 2) and human cell samples (average of all three control cell conditions, n = 6) from the data in panel A and Table S3.