Global Chromatin Profiling (GCP) technology is a mass spectrometry-based assay to identify and quantify post-translational modifications on histone proteins from bulk chromatin (i.e. measuring changes in epigenetic marks on histones). Around 60 different combinations of histone modifications can be quantified on H3, with even more possible combinations on H4, H2A (including isoforms), and H2B.
Chromatin profiling may be thought of as orthogonal to ChIP-Seq. Instead of characterizing one histone mark at a time with locus resolution across the genome, almost all combinations of histone marks are profiled together in bulk chromatin with no genomic resolution. The technique is particularly useful in assessing the functional consequences of genetic mutations to the epigenetic machinery, and has been used to discover novel cancer alleles. Ultimately, it is a signature generation technology that can be employed to make connections among biological conditions and perturbations.