Quantitation of nucleosome acetylation and other histone posttranslational modifications using microscale NU-ELISA.

Histone posttranslational modifications (PTMs) are highly important molecular determinants of epigenetic regulatory mechanisms. Histone PTMs associated with nucleosomes are intimately tied to the transcriptional activity or silence of genes. In addition, nucleosomal PTMs participate in the organization of chromatin into higher-order structures and the progression through mitosis. Changes in histone PTMs are also regulated during the course of mammalian development and are altered in pathological states including cancer. Histone acetyl modifications (and also methylation and phosphorylation) are frequently assayed by western blotting (WB), mass spectrometry (MS), and chromatin immunoprecipitation (ChIP). Here we show that an enzyme-linked immunosorbent assay performed on nucleosomes (NU-ELISA) can quickly and effectively yield quantitative detection of global levels of histone acetylation on small samples such as single human embryonic stem cell colonies. The microscale NU-ELISA method presented here can be performed in most laboratories equipped with basic instrumentation for molecular and cellular biology.