TBP bookmarks and preserves neural stem cell fate memory by orchestrating local chromatin architecture (CUT&Tag)

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 identify the TBP, H2A.Z, ELL and dEP400 distribution pattern, and the relationship between them, we carried out in vivo CUT&Tag assay in Drosophila type II neural stem cells. To find out the genomic loci mitotically bound by hTBP, we isolated mitosis versus interphase neural stem cells and performed anti-hTBP CUT and Tag and identified the binding sites of endogenous TBP in interphase and mitotic neural stem cells respectively. We also found out the genomic loci bound by human H2A.Z and mitotically bound by human TBP in HEK 293T cells by CUT and Tag.