Recruitment of the Histone Variant macroH2A1 to the Pericentric Region Occurs upon Chromatin Relaxation and Is Responsible for Major Satellite Transcriptional Regulation

Heterochromatin formation plays a pivotal role in regulating chromatin organization and influences nuclear architecture, and genome stability and expression. Among the regions at which heterochromatin is present, pericentric regions are known to recruit the histone variant macroH2A1. However, the factors and mechanisms behind macroH2A1 incorporation into these regions have not been explored. In this study, we probe different conditions that lead to the recruitment of macroH2A1 to pericentromeric regions and elucidate its underlying functions. Through experiments conducted on murine fibroblastic cells, we discover that partial chromatin relaxation resulting from DNA damage, senescence or histone hyper-acetylation, is necessary for the recruitment of macroH2A1 to pericentric regions. Furthermore, macroH2A1 is required for up-regulation of noncoding pericentric RNA expression but not for pericentric chromatin organization. Our findings shed light on the functional rather than structural significance of macroH2A1 incorporation into pericentric chromatin.