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Chromosoma Sep 2023During mammalian reproduction, germ cell chromatin packaging is key to prepare parental genomes for fertilization and to initiate embryonic development. While chromatin... (Review)
Review
During mammalian reproduction, germ cell chromatin packaging is key to prepare parental genomes for fertilization and to initiate embryonic development. While chromatin modifications such as DNA methylation and histone post-translational modifications are well known to carry regulatory information, histone variants have received less attention in this context. Histone variants alter the stability, structure and function of nucleosomes and, as such, contribute to chromatin organization in germ cells. Here, we review histone variants expression dynamics during the production of male and female germ cells, and what is currently known about their parent-of-origin effects during reproduction. Finally, we discuss the apparent conundrum behind these important functions and their recent evolutionary diversification.
Topics: Animals; Male; Female; Histones; Chromatin; Nucleosomes; DNA Methylation; Reproduction; Mammals
PubMed: 37347315
DOI: 10.1007/s00412-023-00803-9 -
Circulation Apr 2024Progressive remodeling of cardiac gene expression underlies decline in cardiac function, eventually leading to heart failure. However, the major determinants of...
BACKGROUND
Progressive remodeling of cardiac gene expression underlies decline in cardiac function, eventually leading to heart failure. However, the major determinants of transcriptional network switching from normal to failed hearts remain to be determined.
METHODS
In this study, we integrated human samples, genetic mouse models, and genomic approaches, including bulk RNA sequencing, single-cell RNA sequencing, chromatin immunoprecipitation followed by high-throughput sequencing, and assay for transposase-accessible chromatin with high-throughput sequencing, to identify the role of chromatin remodeling complex INO80 in heart homeostasis and dysfunction.
RESULTS
The INO80 chromatin remodeling complex was abundantly expressed in mature cardiomyocytes, and its expression further increased in mouse and human heart failure. Cardiomyocyte-specific overexpression of , its core catalytic subunit, induced heart failure within 4 days. Combining RNA sequencing, chromatin immunoprecipitation followed by high-throughput sequencing, and assay for transposase-accessible chromatin with high-throughput sequencing, we revealed INO80 overexpression-dependent reshaping of the nucleosomal landscape that remodeled a core set of transcription factors, most notably the MEF2 (Myocyte Enhancer Factor 2) family, whose target genes were closely associated with cardiac function. Conditional cardiomyocyte-specific deletion of in an established mouse model of heart failure demonstrated remarkable preservation of cardiac function.
CONCLUSIONS
In summary, our findings shed light on the INO80-dependent remodeling of the chromatin landscape and transcriptional networks as a major mechanism underlying cardiac dysfunction in heart failure, and suggest INO80 as a potential preventative or interventional target.
Topics: Humans; Animals; Mice; Gene Regulatory Networks; Chromatin Assembly and Disassembly; Chromatin; Myocytes, Cardiac; Heart Failure; RNA; Transposases; ATPases Associated with Diverse Cellular Activities; DNA-Binding Proteins
PubMed: 38152931
DOI: 10.1161/CIRCULATIONAHA.123.065440 -
Nature Genetics Jan 2024Chromatin accessibility is a hallmark of active transcription and entails ATP-dependent nucleosome remodeling, which is carried out by complexes such as...
Chromatin accessibility is a hallmark of active transcription and entails ATP-dependent nucleosome remodeling, which is carried out by complexes such as Brahma-associated factor (BAF). However, the mechanistic links between transcription, nucleosome remodeling and chromatin accessibility are unclear. Here, we used a chemical-genetic approach coupled with time-resolved chromatin profiling to dissect the interplay between RNA Polymerase II (RNAPII), BAF and DNA-sequence-specific transcription factors in mouse embryonic stem cells. We show that BAF dynamically unwraps and evicts nucleosomes at accessible chromatin regions, while RNAPII promoter-proximal pausing stabilizes BAF chromatin occupancy and enhances ATP-dependent nucleosome eviction by BAF. We find that although RNAPII and BAF dynamically probe both transcriptionally active and Polycomb-repressed genomic regions, pluripotency transcription factor chromatin binding confers locus specificity for productive chromatin remodeling and nucleosome eviction by BAF. Our study suggests a paradigm for how functional synergy between dynamically acting chromatin factors regulates locus-specific nucleosome organization and chromatin accessibility.
Topics: Animals; Mice; Transcription Factors; Nucleosomes; Chromatin; RNA Polymerase II; Chromatin Assembly and Disassembly; Adenosine Triphosphate
PubMed: 38049663
DOI: 10.1038/s41588-023-01603-8 -
Genome Research Dec 2023Mammalian sperm show an unusual and heavily compacted genomic packaging state. In addition to its role in organizing the compact and hydrodynamic sperm head, it has been...
Mammalian sperm show an unusual and heavily compacted genomic packaging state. In addition to its role in organizing the compact and hydrodynamic sperm head, it has been proposed that sperm chromatin architecture helps to program gene expression in the early embryo. Scores of genome-wide surveys in sperm have reported patterns of chromatin accessibility, nucleosome localization, histone modification, and chromosome folding. Here, we revisit these studies in light of recent reports that sperm obtained from the mouse epididymis are contaminated with low levels of cell-free chromatin. In the absence of proper sperm lysis, we readily recapitulate multiple prominent genome-wide surveys of sperm chromatin, suggesting that these profiles primarily reflect contaminating cell-free chromatin. Removal of cell-free DNA, and appropriate lysis conditions, are together required to reveal a sperm chromatin state distinct from most previous reports. Using ATAC-seq to explore relatively accessible genomic loci, we identify a landscape of open loci associated with early development and transcriptional control. Histone modification and chromosome folding profiles also strongly support the hypothesis that prior studies suffer from contamination, but technical challenges associated with reliably preserving the architecture of the compacted sperm head prevent us from confidently assaying true localization patterns for these epigenetic marks. Together, our studies show that our knowledge of chromosome packaging in mammalian sperm remains largely incomplete, and motivate future efforts to more accurately characterize genome organization in mature sperm.
PubMed: 38129076
DOI: 10.1101/gr.277845.123 -
Journal of Virology Jul 2023Adeno-associated virus (AAV) is a nonenveloped single-stranded DNA (ssDNA) icosahedral T=1 virus being developed as a vector for clinical gene delivery systems....
Adeno-associated virus (AAV) is a nonenveloped single-stranded DNA (ssDNA) icosahedral T=1 virus being developed as a vector for clinical gene delivery systems. Currently, there are approximately 160 AAV clinical trials, with AAV2 being the most widely studied serotype. To further understand the AAV gene delivery system, this study investigates the role of viral protein (VP) symmetry interactions on capsid assembly, genome packaging, stability, and infectivity. A total of 25 (seven 2-fold, nine 3-fold, and nine 5-fold symmetry interface) AAV2 VP variants were studied. Six 2-fold and two 5-fold variants did not assemble capsids based on native immunoblots and anti-AAV2 enzyme-linked immunosorbent assays (ELISAs). Seven of the 3-fold and seven of the 5-fold variants that assembled capsids were less stable, while the only 2-fold variant that assembled had ~2°C higher thermal stability () than recombinant wild-type AAV2 (wtAAV2). Three of the 3-fold variants (AAV2-R432A, AAV2-L510A, and N511R) had an approximately 3-log defect in genome packaging. Consistent with previous reports of the 5-fold axes, the region of the capsid is important for VP1u externalization and genome ejection, and one 5-fold variant (R404A) had a significant defect in viral infectivity. The structures of wtAAV2 packaged with a transgene (AAV2-full) and without a transgene (AAV2-empty) and one 5-fold variant (AAV2-R404A) were determined by cryo-electron microscopy and three dimensional (3D)-image reconstruction to 2.8, 2.9, and 3.6 Å resolution, respectively. These structures revealed the role of stabilizing interactions on the assembly, stability, packaging, and infectivity of the virus capsid. This study provides insight into the structural characterization and functional implications of the rational design of AAV vectors. Adeno-associated viruses (AAVs) have been shown to be useful vectors for gene therapy applications. Consequently, AAV has been approved as a biologic for the treatment of several monogenic disorders, and many additional clinical trials are ongoing. These successes have generated significant interest in all aspects of the basic biology of AAV. However, to date, there are limited data available on the importance of the capsid viral protein (VP) symmetry-related interactions required to assemble and maintain the stability of the AAV capsids and the infectivity of the AAV capsids. Characterizing the residue type and interactions at these symmetry-driven assembly interfaces of AAV2 has provided the foundation for understanding their role in AAV vectors (serotypes and engineered chimeras) and has determined the residues or regions of the capsid that can or cannot tolerate alterations.
Topics: Capsid; Dependovirus; Serogroup; Cryoelectron Microscopy; Capsid Proteins; Parvovirinae; Viral Proteins; Genetic Vectors; Virus Assembly
PubMed: 37310260
DOI: 10.1128/jvi.01772-22 -
The Journal of Biological Chemistry Sep 2023DNA in eukaryotic cells is packaged into the compact and dynamic structure of chromatin. This packaging is a double-edged sword for DNA repair and genomic stability.... (Review)
Review
DNA in eukaryotic cells is packaged into the compact and dynamic structure of chromatin. This packaging is a double-edged sword for DNA repair and genomic stability. Chromatin restricts the access of repair proteins to DNA lesions embedded in nucleosomes and higher order chromatin structures. However, chromatin also serves as a signaling platform in which post-translational modifications of histones and other chromatin-bound proteins promote lesion recognition and repair. Similarly, chromatin modulates the formation of DNA damage, promoting or suppressing lesion formation depending on the chromatin context. Therefore, the modulation of DNA damage and its repair in chromatin is crucial to our understanding of the fate of potentially mutagenic and carcinogenic lesions in DNA. Here, we survey many of the landmark findings on DNA damage and repair in chromatin over the last 50 years (i.e., since the beginning of this field), focusing on excision repair, the first repair mechanism studied in the chromatin landscape. For example, we highlight how the impact of chromatin on these processes explains the distinct patterns of somatic mutations observed in cancer genomes.
Topics: Chromatin; DNA; DNA Damage; Excision Repair; Nucleosomes
PubMed: 37527775
DOI: 10.1016/j.jbc.2023.105118 -
ELife Mar 2024To find nucleosomes, chromatin remodelers slide and hop along DNA, and their direction of approach affects the direction that nucleosomes slide in.
To find nucleosomes, chromatin remodelers slide and hop along DNA, and their direction of approach affects the direction that nucleosomes slide in.
Topics: Nucleosomes; DNA-Binding Proteins; Saccharomyces cerevisiae Proteins; Chromatin Assembly and Disassembly; Chromatin
PubMed: 38488335
DOI: 10.7554/eLife.96836 -
Nucleic Acids Research Sep 2023The SWI/SNF family of ATP-dependent chromatin remodeling complexes is implicated in multiple DNA damage response mechanisms and frequently mutated in cancer. The BAF,...
The SWI/SNF family of ATP-dependent chromatin remodeling complexes is implicated in multiple DNA damage response mechanisms and frequently mutated in cancer. The BAF, PBAF and ncBAF complexes are three major types of SWI/SNF complexes that are functionally distinguished by their exclusive subunits. Accumulating evidence suggests that double-strand breaks (DSBs) in transcriptionally active DNA are preferentially repaired by a dedicated homologous recombination pathway. We show that different BAF, PBAF and ncBAF subunits promote homologous recombination and are rapidly recruited to DSBs in a transcription-dependent manner. The PBAF and ncBAF complexes promote RNA polymerase II eviction near DNA damage to rapidly initiate transcriptional silencing, while the BAF complex helps to maintain this transcriptional silencing. Furthermore, ARID1A-containing BAF complexes promote RNaseH1 and RAD52 recruitment to facilitate R-loop resolution and DNA repair. Our results highlight how multiple SWI/SNF complexes perform different functions to enable DNA repair in the context of actively transcribed genes.
Topics: Chromatin Assembly and Disassembly; Chromosomal Proteins, Non-Histone; DNA; DNA Repair; Homologous Recombination; R-Loop Structures; Humans
PubMed: 37470997
DOI: 10.1093/nar/gkad609 -
Annual Review of Microbiology Sep 2023, the human malaria parasite, infects two hosts and various cell types, inducing distinct morphological and physiological changes in the parasite in response to... (Review)
Review
, the human malaria parasite, infects two hosts and various cell types, inducing distinct morphological and physiological changes in the parasite in response to different environmental conditions. These variations required the parasite to adapt and develop elaborate molecular mechanisms to ensure its spread and transmission. Recent findings have significantly improved our understanding of the regulation of gene expression in . Here, we provide an up-to-date overview of technologies used to highlight the transcriptomic adjustments occurring in the parasite throughout its life cycle. We also emphasize the complementary and complex epigenetic mechanisms regulating gene expression in malaria parasites. This review concludes with an outlook on the chromatin architecture, the remodeling systems, and how this 3D genome organization is critical in various biological processes.
Topics: Humans; Animals; Chromatin Assembly and Disassembly; Epigenesis, Genetic; Parasites; Chromatin; Malaria, Falciparum
PubMed: 37268002
DOI: 10.1146/annurev-micro-032521-041554 -
Trends in Biochemical Sciences Dec 2023Giant viruses (Nucleocytoviricota) have a largely conserved lifecycle, yet how they cram their large genomes into viral capsids is mostly unknown. The major capsid... (Review)
Review
Giant viruses (Nucleocytoviricota) have a largely conserved lifecycle, yet how they cram their large genomes into viral capsids is mostly unknown. The major capsid protein and the packaging ATPase (pATPase) comprise a highly conserved morphogenesis module in giant viruses, yet some giant viruses dispense with an icosahedral capsid, and others encode multiple versions of pATPases, including conjoined ATPase doublets, or encode none. Some giant viruses have acquired DNA-condensing proteins to compact their genomes, including sheath-like structures encasing folded DNA or densely packed viral nucleosomes that show a resemblance to eukaryotic nucleosomes at the telomeres. Here, we review what is known and unknown about these ATPases and condensing proteins, and place these variations in the context of viral lifecycles.
Topics: Viral Genome Packaging; Nucleosomes; Capsid Proteins; DNA; Adenosine Triphosphatases; Genome, Viral; Virus Assembly
PubMed: 37777391
DOI: 10.1016/j.tibs.2023.09.003