Quantification of nucleosome modifications using chemically-defined recombinant nucleosomes
The invention relates to the use of recombinant/semi-synthetic nucleosomes carrying histone and/or DNA modifications as a reference standard for quantification of covalently modified (on the histone proteins or wrapping DNA), variant, or mutant nucleosomes (collectively “modified nucleosomes” or “nucleosome modifications”) from a biological sample. The invention further relates to methods of using the assay to accurately quantify single or combinatorial nucleosome modifications as biomarkers of disease.
1. A method of determining the specificity of an affinity reagent for a core histone modification and/or DNA modification target epitope, the method comprising using one or more recombinant nucleosomes carrying one or more histone modification and/or DNA modification, wherein determining the specificity of an affinity reagent comprises:
a. preparing one or more recombinant mono- and/or polynucleosome sample comprising nucleosomes carrying the one or more histone modification and/or DNA modification target epitopes;
b. preparing a recombinant mono- and/or polynucleosome sample that does not comprise the one or more histone modification and/or DNA modification target epitopes;
c. providing the recombinant nucleosome sample of (a) and the recombinant nucleosome sample of (b) to create a series of reference standards;
d. adding one or more affinity reagent to the series of reference standards of (c); and
e. performing an affinity reagent-based assay to measure the amount of nucleosome modification in the series of reference standards of (c) and using this information to determine the specificity and background binding of the affinity reagent.
2. The method of claim 1 , wherein the affinity reagent is a detection reagent.
3. The method of claim 1 , wherein the affinity reagent is a capture reagent.
4. The method of claim 1 , wherein the affinity reagent is an antibody, antibody fragment, Fab, Fab′, F(ab)′ 2 , scFv, Fv fragment, nanobody, VHH, aptamer, or non-immunoglobulin scaffold.
5. The method of claim 1 , wherein the affinity reagent-based assay is selected from the group consisting of ELISA, AlphaLISA, AlphaSCREEN, Luminex, and immunoblotting.
6. The method of claim 1 , wherein the affinity reagent-based assay uses two different affinity reagents for substrate capture and detection.
7. The method of claim 6 , wherein the capture and detection reagents specifically bind a histone post-translational modification (PTM) and another nucleosome structure.
8. The method of claim 6 , wherein the capture and detection reagents specifically bind two different histone PTMs.
9. The method of claim 1 , wherein the affinity reagent-based assay uses the same affinity reagent for both substrate capture and detection.
10. The method of claim 1 , wherein the nucleosome comprises at least one post-translational amino acid modification or DNA modification selected from the group consisting of N-acetylation of serine and alanine; phosphorylation of serine, threonine and tyrosine; N-crotonylation, N-acylation of lysine; N6-methylation, N6,N6-dimethylation, N6,N6,N6-trimethylation of lysine; omega-N-methylation, symmetrical-dimethylation, asymmetrical-dimethylation of arginine; citrullination of arginine; ubiquitinylation of lysine; sumoylation of lysine; O-methylation of serine and threonine, ADP-ribosylation of arginine, aspartic acid and glutamic acid; oncogenic K-to-M mutations; 5-methylcytosine, 5-hydroxymethylcytosine, 5-formylcytosine, 5-carboxylcytosine, 3-methylcytosine, 5,6-dihydrouracil, 7-methylguanosine, xanthosine, and inosine.
11. The method of claim 1 , wherein a biological sample is analyzed at the same time as the recombinant nucleosomes.
12. The method of claim 7 , wherein the another nucleosome structure is DNA or unmodified histone.
13. The method of claim 10 , wherein the oncogenic K-to-M mutation is H3K4M, H3K9M, H3K27M, H3G34R, H3G34V, H3G34W, or H3K36M.