Project description:The nucleosome is a fundamental unit of chromatin in eukaryotes, and generally prevents the binding of transcription factors to genomic DNA. Pioneer transcription factors overcome the nucleosome barrier, and bind their target DNA sequences in chromatin. OCT4 is a representative pioneer transcription factor that plays a role in stem cell pluripotency. In the present study, we biochemically analyzed the nucleosome binding by OCT4. Crosslinking mass spectrometry showed that OCT4 binds the nucleosome.
2020-05-13 | PXD019160 | JPOST Repository
Project description:Defining transcription factor nucleosome binding with Pioneer-seq
Project description:Though the in vitro structural and in vivo spatial characteristics of transcription factor (TF) binding are well defined, TF interactions with chromatin and other companion TFs during development are poorly understood. To analyze such interactions in vivo, we profiled several TFs across a time course of human embryonic stem cell differentiation via CUT&RUN epigenome profiling, and studied their interactions with nucleosomes and co-occurring TFs by Enhanced Chromatin Occupancy (EChO), a computational strategy for classifying TF binding characteristics across time and space. EChO shows that at different enhancer targets, the same TF can employ either direct DNA binding, or “pioneer” nucleosome binding to access them. Pioneer binding is correlated with local binding of other TFs and enhancer motif character, including degeneracy at key bases in the pioneer factor target motif. Our strategy reveals a dynamic exchange of TFs at enhancers across developmental time that is aided by pioneer nucleosome binding.
2019-06-25 | GSE128499 | GEO
Project description:The pioneer transcription factor ELF2 remodels the nucleosome near transcription start sites
Project description:Previous unbiased screening for the nucleosome binding affinity of transcription factors predicts that POU domain transcription factors have strong nucleosome binding potential. Here using reprogramming strategy we found that POU4F3 has pioneer factor activity at ATOH1 target elements that require POU4F3 for their accessibility.
Project description:BAF complex is one major group of chromatin remodeling factors in mammals. However, how BAF regulated nucleosomes and other histone modifications is not clear. Here we delete BAF250a, a major component in esBAF to study the nucleosome and histone changes in ESCs. We find that deletion of BAF250a leads to nucleosome occupancy increase in TSS regions and non-pioneer transcription factor binding sites. BAF250a deletion also cause overall decrease of H3K27me3 modification. Collectively, these results reveals how BAF complex coordinates nucleosome, histone modification to control ESC function. Sample 1-4: Nucleosome profiles in WT and BAF250a KO ESCs. Sample 5-10: profiling of H3K4me3 and H3K27me3 in WT and BAF250 KO ESCs.
Project description:Pioneer transcription factors target compact, transcriptionally silent chromatin, thereby enabling gene activation in development, regeneration, and cell reprogramming. However, silent chromatin is heterogenous, varying in nucleosome mobility, nucleosome compaction, and repressive histone modifications, and how pioneer factors may overcome these different chromatin barriers is unknown. We systematically compared the chromatin targeting of 13 embryonic transcription factors and found that the DNA binding domain (DBD) type predicts whether a pioneer factor targets low-turnover nucleosomes in compact chromatin, dynamic nucleosomes in compact chromatin, or function as non-pioneer factors targeting accessible chromatin. By contrast, non-DBD domains enable targeting of repressed chromatin marked by H3K9me3 or H3K27me3. Fusions of different non-DBD segments of heterochromatin-targeting pioneer factors onto SOX2 can expand binding of Sox2 target motifs, including within heterochromatin, and improve cellular reprogramming. Our study unveils how different forms of silent chromatin are coordinately targeted by lineage-specifying factors.
Project description:RFX5 is a DNA binding protein known to regulate MHC genes expressions with little studies on its role in maintaining 3D genome architecture. Recent studies have shown its potential in mediating long-range interactions in specific regions, though the underlying mechanism remains poorly understood. Here, using genes related to cancer progression as a paradigm, we studied the role of RFX5 and found that it specifically regulates these genes. It mediates interactions between gene promoters and their distal enhancers, which can be several hundreds of kilobases apart. We also found that RFX5 regulates higher-order structures of TADs and compartments, which become unstable upon loss of RFX5. Our findings elucidate the fundamental role of RFX5 in maintaining proper chromosome architecture and shed light on the relationship between chromatin loops and gene expression.
Project description:RFX5 is a DNA binding protein known to regulate MHC genes expressions with little studies on its role in maintaining 3D genome architecture. Recent studies have shown its potential in mediating long-range interactions in specific regions, though the underlying mechanism remains poorly understood. Here, using genes related to cancer progression as a paradigm, we studied the role of RFX5 and found that it specifically regulates these genes. It mediates interactions between gene promoters and their distal enhancers, which can be several hundreds of kilobases apart. We also found that RFX5 regulates higher-order structures of TADs and compartments, which become unstable upon loss of RFX5. Our findings elucidate the fundamental role of RFX5 in maintaining proper chromosome architecture and shed light on the relationship between chromatin loops and gene expression.