Xenbase Image ID: 126246

Figure 4. Opposing Histone Modifications on the H3 27-40 peptide in Xenopus embryos.A) Amino-acid sequence of the H3 27-40 peptide and its isobaric modification forms, which have identical mass although beeing differently modified at K27 and K36 residues. Panels B+C - Extracted ion chromatograms (XICs) showing separation of isobaric H3 27–40 peptides from the four Xenopus embryonic stages by differential elution from a C18 micro-column on the reversed-phase HPLC of on-line mass spectrometry. X-axis represents retention time, y-axis the intensity of ion currents in the quadrupole Orbi-Trap mass spectrometer. Peak separation was called by the ICIS peak detection algorithm program (Thermo), indicated here by the vertical black lines. B) XICs of isobaric di-methylated peptides, modified at either K27 or K36. C) XICs of isobaric tri-methylated peptides representing K27me3/K36me3, K27me2+K36me1 and K27me1+K36me2. D) Bar-Chart of H3K27 and K36 modification states. Note that isobaric mono- (data not shown) and tri-methylated peptides, which are methylated either at K27 or K36, elute simultanously and cannot be distinguished. E) Bar-Chart of combinatorial K27/K36-methylated peptides. Abbreviations: unmod  =  unmodified peptide, me1  =  single mono-methylated lysine at position 27 or 36, K27me2  =  di-methylated lysine 27, K36me2  =  di-methylated lysine 36, Kme3  =  single tri-methylated lysine at position 27 or 36, K27me1/K36me1  =  double mono-methylated, K27me2/K36me2  =  double di-methylated, K27me1/K36me2  =  combinatorial triple-methylated peptide with dimethlyted K36, K27me2/K36me1  =  combinatorial triple-methylated peptide with dimethlyted K27. Error bars represent SD. Where applicable, p values are given by numbers above brackets to indicate significant differences in the abundance of a histone modification between samples. Image published in: Schneider TD et al. (2011) Schneider et al. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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