Nucleosome occupancy plays an important role in chromatin compaction, affecting biological processes by hampering the binding of cis-acting elements such as transcription factors, RNA polymerase machinery, and coregulatory. Accessible regions allow for cis-acting elements to bind DNA and regulate transcription. Here, we detail our protocol to profile nucleosome occupancy and chromatin structure dynamics under drought stress at the genome-wide scale using micrococcal nuclease (MNase) digestion. Combining variable MNase concentration treatments and high-throughput sequencing, we investigate the changes in the overall chromatin state using bread wheat samples from an exemplary drought experiment.
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http://dx.doi.org/10.1007/978-1-0716-3973-3_2 | DOI Listing |
Nat Struct Mol Biol
January 2025
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA.
Transcription activators are said to stimulate gene expression by 'recruiting' coactivators, yet this vague term fits multiple kinetic models. To directly analyze the dynamics of activator-coactivator interactions, single-molecule microscopy was used to image promoter DNA, a transcription activator and the Spt-Ada-Gcn5 acetyltransferase (SAGA) complex within yeast nuclear extract. SAGA readily but transiently binds nucleosome-free DNA without an activator, while chromatin association occurs primarily when an activator is present.
View Article and Find Full Text PDFNat Commun
January 2025
Friedrich Miescher Institute for Biomedical Research, Fabrikstrasse 24, 4056, Basel, Switzerland.
In the germ line and during early embryogenesis, DNA methylation (DNAme) undergoes global erasure and re-establishment to support germ cell and embryonic development. While DNAme acquisition during male germ cell development is essential for setting genomic DNA methylation imprints, other intergenerational roles for paternal DNAme in defining embryonic chromatin are unknown. Through conditional gene deletion of the de novo DNA methyltransferases Dnmt3a and/or Dnmt3b, we observe that DNMT3A primarily safeguards against DNA hypomethylation in undifferentiated spermatogonia, while DNMT3B catalyzes de novo DNAme during spermatogonial differentiation.
View Article and Find Full Text PDFJ Chem Phys
January 2025
Department of Physics and Astronomy and Center for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854, USA.
Nucleosomes are fundamental units of chromatin in which a length of genomic DNA is wrapped around a histone octamer spool in a left-handed superhelix. Large-scale nucleosome maps show a wide distribution of DNA wrapping lengths, which in some cases are tens of base pairs (bp) shorter than the 147 bp canonical wrapping length observed in nucleosome crystal structures. Here, we develop a thermodynamic model that assumes a constant free energy cost of unwrapping a nucleosomal bp.
View Article and Find Full Text PDFbioRxiv
December 2024
Department of Biochemistry and Molecular Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
A major challenge in epigenetics is uncovering the dynamic distribution of nucleosomes and other DNA-binding proteins, which plays a crucial role in regulating cellular functions. Established approaches such as ATAC-seq, ChIP-seq, and CUT&RUN provide valuable insights but are limited by the ensemble nature of their data, masking the cellular and molecular heterogeneity that is often functionally significant. Recently, long-read sequencing technologies, particularly Single Molecule, Real-Time (SMRT/PacBio) sequencing, have introduced transformative capabilities, such as N-methyladenine (6mA) footprinting.
View Article and Find Full Text PDFNature
December 2024
Institute of Regeneration and Repair, Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, UK.
Cellular identity requires the concerted action of multiple transcription factors (TFs) bound together to enhancers of cell-type-specific genes. Despite TFs recognizing specific DNA motifs within accessible chromatin, this information is insufficient to explain how TFs select enhancers. Here we compared four different TF combinations that induce different cell states, analysing TF genome occupancy, chromatin accessibility, nucleosome positioning and 3D genome organization at the nucleosome resolution.
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