Magic™ Anti-Histone H2A.x (phospho S139) polyclonal antibody

Facilitates chromatin transcription (FACT) is a histone chaperone, which accomplishes both nucleosome assembly and disassembly. Our combined cryo-electron microscopy (EM) and native mass spectrometry (MS) studies revealed novel key steps of nucleosome reorganization conducted by a Mid domain and its adjacent acidic AID segment of human FACT. We determined three cryo-EM structures of respective octasomes complexed with the Mid-AID and AID regions, and a hexasome alone. We discovered extensive contacts between a FACT region and histones H2A, H2B, and H3, suggesting that FACT is competent to direct functional replacement of a nucleosomal DNA end by its phosphorylated AID segment (pAID). Mutational assays revealed that the aromatic and phosphorylated residues within pAID are essential for octasome binding. The EM structure of the hexasome, generated by the addition of Mid-pAID or pAID, indicated that the dissociation of H2A-H2B dimer causes significant alteration from the canonical path of the nucleosomal DNA.

The cellular response to DNA damage protects the essential information stored in the genome. This mechanism is crucial in terms of the cancer prevention and aging progression. The DNA damage response (DDR) consists of a complex network controlling the cell cycle and multiple mechanisms of the DNA repair. The DDR disruption is a cornerstone feature of the tumor cells, which allows them to enhance beneficial mutations that prevent successful disease treatment. The important checkpoints of the DDR are currently poorly understood due to the complexity and diversity of the DNA repair machinery. Histone ubiquitination is intensively involved in the repair of the double-stranded DNA breaks. This post-translational modification is known to be a key factor in the recruitment of the repair factors to the DNA damage sites. Here, the crucial role of the ubiquitin lysine residue K27 in the process of histone H2A monoubiquitination mediated by the ubiquitin ligase RNF168 has been showed. The presented data suggest forced and intensive diffusion of ubiquitin from the cytoplasm to the nucleus, which is characterized by the dynamic equilibrium less than 10 min. The comparison of the turnover rate of the wild-type ubiquitin and its variant with a single functional lysine residue K27 suggests an important role of the ubiquitin deposition as a covalent conjugate with histone H2A in terms of the stability of the entire ubiquitinome.