Catalytic-dependent and independent functions of the histone acetyltransferase CBP promote pioneer factor-mediated zygotic genome activation [CUT&Tag]

Immediately after fertilization the genome is transcriptionally quiescent. Maternally encoded pioneer transcription factors reprogram the chromatin state and facilitate the transcription of the zygotic genome. In Drosophila, transcription is initiated by the pioneer factor Zelda. While Zelda-occupied sites are enriched with histone acetylation, a post-translational mark associated with active cis-regulatory regions, the functional relationship between Zelda and histone acetylation in zygotic genome activation remained unclear. We show that Zelda-mediated recruitment of the histone acetyltransferase CBP is essential for zygotic transcription and embryonic development. CBP catalytic activity is necessary for release of RNA Polymerase II (Pol II) into transcription elongation. However, CBP largely activates zygotic transcription independent of acetylation through Pol II recruitment. Neither acetylation nor CBP are required for the pioneering function of Zelda. Our data suggest that pioneer factor-mediated recruitment of CBP is a conserved mechanism required to activate zygotic transcription but that this role is separable from the function of pioneer factors in restructuring chromatin accessibility. Overall design: This data set contains CUT&Tag data from the bulk Drosophila melanogaster embryos 2-3 hours after egg laying (AEL) (nuclear cycle 14) during the maternal-to-zygotic transition. CUT&Tag was executed on GFP-CBP;his2AV-RFP (control) and GFP-CBP;nos-deGrad/+;his2AV-RFP embryos to measure the effect CBP knockdown has on level and distribution of chromatin marks. CRY2-CBP;his2av-RFP were treated with blue light to inactivate CBP catalytic activity via the CRY2 optogenetic tag or left in the dark as a control to assay the function of CBP mediated acetylation during ZGA. To corroborate the assay of the catalytic function we used an orthogonal approach with a catalytic mutant CBPHAT (F2161A); the mutant protein is exclusively loaded in embryos with the help of Dominant Female Sterile technique to produce germline clones, compared to a control line (w1118).