Abstract
Human histone H2A.B (formerly H2A.Bbd), a non-allelic H2A variant, exchanges rapidly as compared to canonical H2A, and preferentially associates with actively transcribed genes. We found that H2A.B transiently accumulated at DNA replication and repair foci in living cells. To explore the biochemical function of H2A.B, we performed nucleosome reconstitution analyses using various lengths of DNA. Two types of H2A.B nucleosomes, octasome and hexasome, were formed with 116, 124, or 130 base pairs (bp) of DNA, and only the octasome was formed with 136 or 146 bp DNA. In contrast, only hexasome formation was observed by canonical H2A with 116 or 124 bp DNA. A small-angle X-ray scattering analysis revealed that the H2A.B octasome is more extended, due to the flexible detachment of the DNA regions at the entry/exit sites from the histone surface. These results suggested that H2A.B rapidly and transiently forms nucleosomes with short DNA segments during chromatin reorganization.
Highlights
Human histone H2A.B, a non-allelic H2A variant, exchanges rapidly as compared to canonical H2A, and preferentially associates with actively transcribed genes
These results suggested that H2A.B rapidly and transiently forms nucleosomes with short DNA segments during chromatin reorganization
H2A.B tagged with the green fluorescent protein (GFP) is highly mobile, as compared to the canonical H2A tagged with GFP25
Summary
Human histone H2A.B (formerly H2A.Bbd), a non-allelic H2A variant, exchanges rapidly as compared to canonical H2A, and preferentially associates with actively transcribed genes. A small-angle X-ray scattering analysis revealed that the H2A.B octasome is more extended, due to the flexible detachment of the DNA regions at the entry/ exit sites from the histone surface These results suggested that H2A.B rapidly and transiently forms nucleosomes with short DNA segments during chromatin reorganization. A small-angle X-ray scattering analysis revealed that the H2A.B octasome structure contained extra volumes on both sides of the nucleosome, as compared to the canonical H2A octasome, probably reflecting the flexible DNA segments at the entry/exit sites. These data suggested that H2A.B may form an intermediate nucleosome with a shorter DNA segment, when chromatin is newly formed or reorganized after DNA replication, repair, and transcription
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