Genetic complementation analysis revealed distinct contributions of the N-terminal tail of H2A.Z to epigenetic regulations

The histone variant H2A.Z is one of the most evolutionally conserved histone variants. In vertebrates, two isoforms, H2A.Z.1 and H2A.Z.2, are identified and are involved in multiple epigenetic regulations. However, the role of H2A.Z in epigenetic regulations largely remains unknown especially in vertebrate. Previously, we derived tetracycline-inducible H2A.Z isofmrs double knockout (DKO) cells by using DT40 cells. With this cell, we showed that H2A.Z DKO leads to defects in mitotic progression and gene expression. To elucidate the function of H2A.Z further, we established genetic complementation system and confirmed that introducing exogenous H2A.Z complemented phenotypes of H2A.Z DKO cells. Given that acetylation of the N-terminal tail of H2A.Z reportedly contributes to significant roles in H2A.Z functions, we introduced two types of H2A.Z mutants, non-acetylable H2A.Z (5KR-H2A.Z) and chimeric H2A.Z in which its N-terminal tail is replaced with that of canonical H2A (H2A-H2A.Z), into H2A.Z DKO cells. These H2A.Z mutants complemented defects in mitotic progression. However, significant transcriptional dysregulation was observed in H2A.Z DKO cells stably expressing 5KR-H2A.Z and H2A-H2A.Z. These results suggest that the core domain and the N-terminal tail of the vertebrate H2A.Z contribute individually to mitotic progression and transcription regulation, respectively. DT40 wild-type (WT) cells, H2A.Z DKO cells and DKO cells stably expressing exogenous H2A.Z.1 or its mutants (5KR-H2A.Z and H2A-H2A.Z) were cultured in the presence of tetracycline for 72 hours. Total RNAs were extracted with the RNeasy mini kit (QIAGEN) according to the manufacture’s protocol. 100 ng of total RNAs was processed for microarray by using the Agilent expression array (Agilent).