Mechanisms of transcriptional repression in Drosophila embryo development
Final Report Abstract
Control of gene expression by transcriptional repression is highly conserved in evolution and plays an important role in key biological processes including the generation of different cell types during embryonic development. To better understand the largely unknown mechanistic principles by which repression is achieved we studied in subproject 1 the mechanisms of transcriptional repression by comprehensively resolving differential transcriptional and chromatin states during Drosophila dorsoventral (DV) patterning. We figure out that whereas Dorsal-mediated repression is accompanied by Polycomb-Group silencing and H3K27me3, repression by Snail involves prevention of H3K27ac without induction of H3K27me3, but both mechanisms impair the release of paused RNA Polymerase II into elongation which is a major regulatory step in tissue-specific DV transcription. In subproject 2, we developed and enhanced an epigenetic engineering system in the fly to learn more about the role of corepressors (HDAC) / co-activators (CBP) during transcriptional repression. The targeted acetylation/deacetylation of regulatory regions in the genome by epi-effectors with histone acetyltransferase (CBP) and deacetylase (HDAC) activity, respectively, leads to the activation/repression of some but not all genes. In addition (subproject 3), we have succeeded in generating flies with fluorescently labelled dorsal fusion proteins by CRISPR/Cas9-mediated genome editing, which can be used to study proteins involved in repression. Since (additional subproject 4) the therapeutic use of HDAC inhibitors, which leads to a relief of transcriptional repression, has shown promising results in the treatment of haematological cancers such as acute myeloid leukaemia (AML), we investigated the differences in gene expression signatures (PRO-Seq) and chromatin states (CUT&Tag) between haematological stem cells from healthy donors and AML patients and their different responses to treatment with epigenetic inhibitors. Preliminary results show that a short HDAC inhibition already leads to a rapid change in the expression and acetylation level (H3K27ac) of some genes.
Publications
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Comprehensive interrogation of aDrosophilaembryonic patterning network reveals the impact of chromatin state on tissue-specific burst kinetics and RNA Polymerase II promoter-proximal pause release. Cold Spring Harbor Laboratory.
Hunt, George; Vaid, Roshan; Pirogov, Sergei; Pfab, Alexander; Ziegenhain, Christoph; Sandberg, Rickard; Reimegård, Johan & Mannervik, Mattias
