Project description:A large fraction of plant genomes is composed of transposable elements (TE), which provide a potential source of novel genes through “domestication” – the process whereby the proteins encoded by TE diverge in sequence, lose their ability to catalyse transposition and instead acquire novel functions for their hosts. In Arabidopsis, ANTAGONIST OF LIKE HETEROCHROMATIN PROTEIN 1 (ALP1) arose by domestication of the nuclease component of Harbinger class TE and acquired a new function as a component of POLYCOMB REPRESSIVE COMPLEX 2 (PRC2), a histone H3K27me3 methyltransferase involved in regulation of host genes and in some cases TE. It was not clear how ALP1 associated with PRC2, nor what the functional consequence was. Here, we identify ALP2 genetically as a suppressor of Polycomb-group (PcG) mutant phenotypes and show that it arose from the second, DNA binding component of Harbinger transposases. Molecular analysis of PcG compromised backgrounds reveals that ALP genes oppose silencing and H3K27me3 deposition at key PcG target genes. Proteomic analysis reveals that ALP1 and ALP2 are components of a variant PRC2 complex that contains the four core components but lacks plant-specific accessory components such as the H3K27me3 reader LIKE HETEROCHROMATION PROTEIN 1 (LHP1). We show that the N-terminus of ALP2 interacts directly with ALP1, whereas the C-terminus of ALP2 interacts with MULTICOPY SUPPRESSOR OF IRA1 (MSI1), a core component of PRC2. Proteomic analysis reveals that in alp2 mutant backgrounds ALP1 protein no longer associates with PRC2, consistent with a role for ALP2 in recruitment of ALP1. We suggest that the propensity of Harbinger TE to insert in gene-rich regions of the genome, together with the modular two component nature of their transposases, has predisposed them for domestication and incorporation into chromatin modifying complexes.
Project description:Elucidation of multivalent interactions involving both DNA and histone post-translational-modifications (PTMs) is essential for providing insight into complex biological functions. We report here the high resolution crystal structure of the N-terminal triple reader module (PHD-Bromo-PWWP) of ZMYND8, which forms a stable unit, capable of simultaneously recognizing histone PTMs and providing a charged platform for DNA interaction. Monte Carlo simulations provide a model whereby the reader module directly engages the core nucleosome particle, extracting the entire histone H3 tail and initiating contacts with the DNA super-coil structure. Systematic mutation of these interaction interfaces reveals cooperativity within the ensemble. Single domain disruption destroys the functional network of interactions initiated by ZMYND8, which impairs recruitment to sites of DNA damage and alters transcription. Taken together, our results establish an important role of the ZMYND8 multivalent reader module in nucleosome binding and chromatin function.
Project description:The ability of cells to perceive and translate versatile cues into differential chromatin and transcriptional states is critical for many biological processes1-4. In plants, timely transition to a flowering state is crucial for successful reproduction5-7. EARLY BOLTING IN SHORT DAY (EBS) is a negative transcriptional regulator that prevents premature flowering in Arabidopsis8,9. Here, we revealed that bivalent bromo-adjacent homology (BAH)-plant homeodomain (PHD) reader modules of EBS bind H3K27me3 and H3K4me3, respectively. A subset of EBS-associated genes was co-enriched with H3K4me3, H3K27me3, and the Polycomb repressor complex 2 (PRC2). Interestingly, EBS adopts an auto-inhibition mode to mediate its binding preference switch between H3K27me3 and H3K4me3. This binding balance is critical because disruption of either EBS-H3K27me3 or EBS-H3K4me3 interaction induces EBS-mediated early floral transition. This study identifies a single bivalent chromatin reader capable of recognizing two antagonistic histone marks and reveals a distinct mechanism of interplay between active and repressive chromatin states.The ability of cells to perceive and translate versatile cues into differential chromatin and transcriptional states is critical for many biological processes1-4. In plants, timely transition to a flowering state is crucial for successful reproduction5-7. EARLY BOLTING IN SHORT DAY (EBS) is a negative transcriptional regulator that prevents premature flowering in Arabidopsis8,9. Here, we revealed that bivalent bromo-adjacent homology (BAH)-plant homeodomain (PHD) reader modules of EBS bind H3K27me3 and H3K4me3, respectively. A subset of EBS-associated genes was co-enriched with H3K4me3, H3K27me3, and the Polycomb repressor complex 2 (PRC2). Interestingly, EBS adopts an auto-inhibition mode to mediate its binding preference switch between H3K27me3 and H3K4me3. This binding balance is critical because disruption of either EBS-H3K27me3 or EBS-H3K4me3 interaction induces EBS-mediated early floral transition. This study identifies a single bivalent chromatin reader capable of recognizing two antagonistic histone marks and reveals a distinct mechanism of interplay between active and repressive chromatin states.v
Project description:Histone methyltransferase SETD1A is critical for acute myeloid leukemia (AML) cell survival, but the molecular mechanism driving SETD1A gene regulation remains elusive. To delineate the role of SETD1A, we utilize a protein degrader technology to induce rapid SETD1A degradation in AML cell lines. SETD1A degradation results in immediate downregulation of transcripts associated with DNA repair and heme biosynthesis pathways. CRISPR-based functional analyses and metabolomics reveal an essential role of SETD1A to maintain mitochondrial respiration in AML cells. These SETD1A targets are enriched in head-to-head (H2H) genes. SETD1A degradation disrupts a non-enzymatic SETD1A domain-dependent cyclin K function, increases the Ser5P RNA polymerase II (RNAP2) at TSS, and induces the promoter-proximal pausing of RNAP2 in a strand-specific manner. This study reveals a non-enzymatic role for SETD1A in transcriptional pause release and provides insight into the mechanism of RNAP2 pausing and its function in cancer.
Project description:This is an investigation of whole genome gene expression level in tissues of mice stimulated by LPS, FK565 or LPS + FK565 in vivo and ex vivo. We show that parenteral administration of a pure synthetic Nod1 ligand, FK565, induces site-specific vascular inflammation in mice, which is prominent in aortic root including aortic valves, slight in aorta and absent in other arteries. The degree of respective vascular inflammation is associated with persistent high expression of proinflammatory chemokine/cytokine genes in each tissue in vivo by microarray analysis, and not with Nod1 expression levels. The ex vivo production of proinflammatory chemokine/cytokine by Nod1 ligand is higher in aortic root than in other arteries from normal murine vascular tissues, and also higher in human coronary artery endothelial cells (HCAEC) than in human pulmonary artery endothelial cells (HPAEC), suggesting that site-specific vascular inflammation is at least in part ascribed to an intrinsic nature of the vascular tissue/cell itself.
Project description:Recognition of post-translational modifications on histones by epigenetic readers is a fundamental mechanism for the regulation of chromatin and transcription. Compared to the large number of readers that recognize histone methylation, only a few acetyllysine readers have been identified, including bromodomain, YEATS, and double plant homeodomain zinc finger (DPF). Here, we report the identification of a novel reader of histone H3, the ZZ-type zinc finger (ZZ) domain of ZZZ3, a subunit of the Ada-Two-A Containing (ATAC) histone acetyltransferase complex. The solution NMR structure of the ZZ in complex with the H3 peptide reveals a unique histone-binding mechanism involving caging of the N-terminal Alanine 1 of histone H3 in an acidic cavity of the ZZ domain. Importantly, acetylation on Lysine 4 of H3 (H3K4ac) enhances the binding, and in cells, ZZZ3 colocalizes with H3K4ac across the genome. The recognition of histone acetylation by ZZ is essential for chromatin occupancy of ZZZ3 and functions of the ATAC complex. Depletion of ZZZ3 or disruption of the ZZ-H3 interaction dampens ATAC dependent promoter histone H3K9 acetylation and the expression of ribosomal protein encoding genes. Overall, our study identifies the ZZ domain of ZZZ3 as a novel epigenetic reader that links the GCN5/ATAC complex to histone acetylation.