The study of histone variants and histone posttranslational modifications (PTMs) is a trending topic in different fields including developmental biology, neurobiology, and immunology; as well as in the understanding of molecular mechanisms leading to diverse diseases, such as cancer. Since the establishment of histone PTMs starts immediately after their synthesis and it continues once they are assembled into chromatin, here we describe a classic protocol of subcellular fractionation aiming to study histones at different stages of maturation. This includes newly synthesized histones enriched in cytosolic fractions; a pool of newly synthesized, evicted, and stored histones enriched in nuclear soluble fractions; and chromatin-associated histones enriched in chromatin pellet. To study specific histone variants and the establishment of their PTMs, we describe a protocol for obtaining histone variants expressed in bacteria. In addition, we describe a Triton-Acetic acid-Urea (TAU) gel electrophoresis protocol adapted to work on mini-gels, which can be coupled to Western blot to analyze PTMs on histone variants. Finally, we describe a Chromatin immunoprecipitation (ChIP) assay for studying histone PTMs, or tagged histone variants, on specific DNA sequences.
Keywords: Acid extraction; ChIP; Histone purification; Histone variants; Histones; PTMs; Recombinant histones; TAU gel electrophoresis.