Project description:The nuclear factor Dek is notably enriched within chromatin; nevertheless, the precise binding mechanism of Dek to the nucleosome remains elusive. In this study, we employ cryo-electron microscopy (cryo-EM) to elucidate the high-resolution structure of the Dek-Nucleosome Core Particle (NCP) complex. We identify specific domains responsible for DEK interaction with the histone octamer and DNA within the nucleosome. The veracity of these binding domains is confirmed through a series of meticulous biochemical experiments. Subsequently, cellular experiments reveal that Dek lacking nucleosome-binding capacity exhibits a deficiency in chromatin interaction. Remarkably, this impairment induces a shift towards the primitive endoderm fate in mouse embryonic stem cells, underscoring the pivotal role of Dek in determining cell fate through its nucleosomal interactions.
Project description:The nuclear factor Dek is notably enriched within chromatin; nevertheless, the precise binding mechanism of Dek to the nucleosome remains elusive. In this study, we employ cryo-electron microscopy (cryo-EM) to elucidate the high-resolution structure of the Dek-Nucleosome Core Particle (NCP) complex. We identify specific domains responsible for DEK interaction with the histone octamer and DNA within the nucleosome. The veracity of these binding domains is confirmed through a series of meticulous biochemical experiments. Subsequently, cellular experiments reveal that Dek lacking nucleosome-binding capacity exhibits a deficiency in chromatin interaction. Remarkably, this impairment induces a shift towards the primitive endoderm fate in mouse embryonic stem cells, underscoring the pivotal role of Dek in determining cell fate through its nucleosomal interactions.
Project description:The nucleosome acidic patch is a major interaction hub for chromatin, providing a platform for enzymes to dock and orient for nucleosome-targeted activities. In order to define the molecular basis of acidic patch recognition proteome-wide, we performed an amino acid resolution acidic patch interactome screen. We discovered that the histone H3 lysine 36 (H3K36) demethylase KDM2A, but not its closely related paralog, KDM2B, requires the acidic patch for nucleosome binding. These KDM2 family JumonjiC (JmjC) domain lysine demethylases are critical to heterochromatin formation and are commonly misregulated in cancer. Despite fundamental roles in transcriptional regulation in health and disease, the molecular mechanisms governing nucleosome substrate specificity of KDM2A/B, or any other JmjC lysine demethylases, remain unclear. We used a covalent JmjC inhibitor to solve cryo-EM structures of KDM2A and KDM2B trapped in action on the nucleosome. Our structures show that KDM2-nucleosome binding is paralog-specific and facilitated by dynamic nucleosomal DNA unwrapping and histone charge shielding that mobilize the H3K36 sequence for demethylation.
Project description:The SWR1 chromatin remodeling complex (SRCAP in humans) is recruited to +1 nucleosomes downstream of transcription start sites of eukaryotic promoters, where it exchanges histone H2A for the specialized variant H2A.Z. Here we use cryo-EM to resolve the structural basis of the SWR1 interaction with free DNA, revealing a distinct open conformation of the Swr1 ATPase that enables sliding from accessible DNA to nucleosomes. A complete structural model of the SWR1-nucleosome complex illustrates critical structure-function roles for Swc2 and Swc3 subunits in oriented nucleosome engagement by SWR1. Moreover, an extended DNA-binding α -helix within the Swc3 subunit enables sensing of nucleosome linker length and is essential for SWR1 promoter-specific recruitment and activity. The previously unresolved N-SWR1 subcomplex forms a flexible extended structure enabling multivalent recognition of acetylated histone tails by reader domains to further direct SWR1 towards the +1 nucleosome. Altogether, our findings provide a generalizable mechanism for promoter-specific targeting of chromatin and transcription complexes.
Project description:Nuclear protein DEK is an endogenous DNA-binding chromatin factor regulating hematopoiesis. DEK is one of only two known secreted nuclear chromatin factors, but whether and how extracellular DEK regulates hematopoiesis is not known. We demonstrate that extracellular DEK greatly enhances ex vivo expansion of cytokine-stimulated human and mouse hematopoietic stem cells, and regulates hematopoiesis in vivo and in vitro. These effects are mediated through chemokine receptor CXCR2 and heparan sulfate proteoglycans, and are associated with enhanced phosphorylation of ERK1/2, AKT and p38 MAPK. Thus, DEK acts as a hematopoietic cytokine, with potential for clinical applicability.