Symmetrical modification within a nucleosome is not required globally for histone lysine methylation

Life Science College, Beijing Normal University, Beijing 100875, China.
EMBO Reports (Impact Factor: 9.06). 02/2011; 12(3):244-51. DOI: 10.1038/embor.2011.6
Source: PubMed


Two copies of each core histone exist in every nucleosome; however, it is not known whether both histones within a nucleosome are required to be symmetrically methylated at the same lysine residues. We report that for most lysine methylation states, wild-type histones paired with mutant, unmethylatable histones in mononucleosomes have comparable methylation levels to bulk histones. Our results indicate that symmetrical histone methylation is not required on a global scale. However, wild-type H4 histones paired with unmethylatable H4K20R histones showed reduced levels of H4K20me2 and H4K20me3, suggesting that some fractions of these modifications might exist symmetrically, and enzymes mediating these modifications might, to some extent, favour nucleosome substrates with premethylated H4K20.

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Available from: She Chen, Jan 11, 2015
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    • "Identification of histone modifications histone paired with wild type. Results demonstrated that lysine methylation levels were very similar between the two types of pairs, indicating that methylation states of histone copies within the nucleosome do not need to be symmetrical, although exceptions could exist (Chen et al., 2011). A later study employed site-specific antibodies and bottom-up MS to directly demonstrate that both symmetrically and asymmetrically modified nucleosomes exist. "
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    • "Addressing the status of histone PTMs on sister histones has so far been hampered by the absence of adequate techniques. A recent report showed that H3 can be methylated at H3K27 even if the sister histone within a nucleosome carries a K27A mutation, which was interpreted as an indication of nucleosome asymmetry (Chen et al., 2011). We suggest that this observation reflects the capability of the enzyme to methylate such a substrate, but may not allow conclusions regarding the in vivo symmetry state. "
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    • "The top six abundant ions were fragmented by collision-induced dissociation, and the fragmented ions were scanned with an ion trap. MS/MS spectra for all distinct methylation states were verified according to our previous reports (Chen et al, 2011; Yuan et al, 2011). Mascot search results were analysed with MSquant, and the ratio of heavy/light peptide pairs was calculated based on the extracted ion chromatogram (Mortensen et al, 2010). "
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