H2A.Z and H3.3 Histone Variants Affect Nucleosome Structure: Biochemical and Biophysical Studies

摘要

Histone variants play important roles in regulation of chromatin structure and function. Tonunderstand the structural role played by histone variants H2A.Z and H3.3, both of which are implicated inntranscription regulation, we conducted extensive biochemical and biophysical analysis on mononucleosomesnreconstituted from either random-sequence DNA derived from native nucleosomes or a defined DNAnnucleosome positioning sequence and recombinant human histones. Using established electrophoretic andnsedimentation analysis methods, we compared the properties of nucleosomes containing canonical histonesnand histone variants H2A.Z and H3.3 (in isolation or in combination).We find only subtle differences in thencompaction and stability of the particles. Interestingly, both H2A.Z and H3.3 affect nucleosome positioning,neither creating new positions or altering the relative occupancy of the existing nucleosome position space. Onnthe other hand, only H2A.Z-containing nucleosomes exhibit altered linker histone binding. These propertiesncould be physiologically significant as nucleosome positions and linker histone binding partly determinenfactor binding accessibility.