TBP bookmarks and preserves neural stem cell fate memory by orchestrating local chromatin architecture (ATAC-Seq)

Mitotic bookmarking has been posited as an important strategy for cells to faithfully propagate their fate memory though cell generations. However, the physiological significance and regulatory mechanisms of mitotic bookmarking in neural development remain unexplored. Here, we identified TBP (TATA binding protein) as a crucial mitotic bookmarker for preserving fate memory of Drosophila neural stem cells (NSCs). Phosphorylation by the super elongation complex (SEC) is important for TBP to retain as discrete foci at mitotic chromosomes of NSCs to effectively transmit their fate memory. TBP depletion leads to drastic NSC loss, whereas TBP overexpression enhances the ability of SEC to induce neural progenitor dedifferentiation and tumorigenesis. Importantly, TBP achieves its mitotic retention through recruiting the chromatin remodeler EP400, which in turn increases local chromatin accessibility via depositing H2A.Z. Thus, local chromatin remodeling ensures mitotic bookmarking, which may represent a general principle underlying the preservation of cell fate memory. Overall design: To assess chromatin architecture of neural stem cells in mitosis, we next performed in vivo ATAC-seq with asynchronous versus mitotic neural stem cells. To investigate whether dEP400 facilitates TBP mitotic retention by increasing local chromatin accessibility, we carried out in vivo ATAC-seq assays.