PT  - JOURNAL ARTICLE
AU  - Hiroaki Tachiwana
AU  - Mariko Dacher
AU  - Kazumitsu Maehara
AU  - Akihito Harada
AU  - Yasuyuki Ohkawa
AU  - Hiroshi Kimura
AU  - Hitoshi Kurumizaka
AU  - Noriko Saitoh
TI  - Chromatin structure-dependent histone incorporation revealed by a genome-wide deposition assay
AID  - 10.1101/641381
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 641381
4099  - http://biorxiv.org/content/early/2019/05/17/641381.short
4100  - http://biorxiv.org/content/early/2019/05/17/641381.full
AB  - Histone proteins, including their variants, play indispensable roles in chromatin structure and function. The incorporation of specific histones is the key to epigenetic features and contributes to cell differentiation and development. To understand how each histone is targeted to and incorporated into a specific chromatin region, we introduced epitope-tagged histone complexes into permeabilized cells and allowed them to become incorporated into the chromatin. The newly incorporated histone complex is easily distinguished from the parental histones by the epitope-tag. We analyzed the correlation between the histone incorporation and the chromatin structure, using the H2A-H2B and H2A.Z-H2B complexes. The histone incorporation mainly occurred at less condensed chromatin (open), suggesting that the condensed chromatin (closed) is a barrier for histone incorporation. To overcome this barrier, H2A, but not H2A.Z, uses a replication-coupled deposition mechanism. This leads to the genome-wide distribution of H2A and the exclusion of H2A.Z from the closed chromatin. Moreover, H2A.Z-H2B is specifically incorporated into the chromatin around the transcription start sites. However, the H2A.Z mutant, in which the H2A.Z-specific region (M6) is swapped with the corresponding H2A residues, is incorporated into the closed chromatin in a replication-coupled manner. The mutant no longer functions as H2A.Z, in terms of the deposition. This may be the reason why the mutant does not compensate for the lethality of the H2A.Z knockout in flies. Our results show that histone incorporations are regulated by the chromatin structures, which may be crucial for maintaining the epigenetic chromatin states.