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Nature Reviews. Molecular Cell Biology Feb 2021Evidence accumulated over the past decade shows that long non-coding RNAs (lncRNAs) are widely expressed and have key roles in gene regulation. Recent studies have begun... (Review)
Review
Evidence accumulated over the past decade shows that long non-coding RNAs (lncRNAs) are widely expressed and have key roles in gene regulation. Recent studies have begun to unravel how the biogenesis of lncRNAs is distinct from that of mRNAs and is linked with their specific subcellular localizations and functions. Depending on their localization and their specific interactions with DNA, RNA and proteins, lncRNAs can modulate chromatin function, regulate the assembly and function of membraneless nuclear bodies, alter the stability and translation of cytoplasmic mRNAs and interfere with signalling pathways. Many of these functions ultimately affect gene expression in diverse biological and physiopathological contexts, such as in neuronal disorders, immune responses and cancer. Tissue-specific and condition-specific expression patterns suggest that lncRNAs are potential biomarkers and provide a rationale to target them clinically. In this Review, we discuss the mechanisms of lncRNA biogenesis, localization and functions in transcriptional, post-transcriptional and other modes of gene regulation, and their potential therapeutic applications.
Topics: Animals; Gene Expression Regulation; Humans; Immune System Diseases; Neoplasms; Neurodevelopmental Disorders; RNA, Long Noncoding; Signal Transduction
PubMed: 33353982
DOI: 10.1038/s41580-020-00315-9 -
Nature Reviews. Genetics Dec 2022Extrachromosomal DNA (ecDNA) amplification is an important driver alteration in cancer. It has been observed in most cancer types and is associated with worse patient... (Review)
Review
Extrachromosomal DNA (ecDNA) amplification is an important driver alteration in cancer. It has been observed in most cancer types and is associated with worse patient outcome. The functional impact of ecDNA has been linked to its unique properties, such as its circular structure that is associated with altered chromatinization and epigenetic regulatory landscape, as well as its ability to randomly segregate during cell division, which fuels intercellular copy number heterogeneity. Recent investigations suggest that ecDNA is structurally more complex than previously anticipated and that it localizes to specialized nuclear bodies (hubs) and can act in trans as an enhancer for genes on other ecDNAs or chromosomes. In this Review, we synthesize what is currently known about how ecDNA is generated and how its genetic and epigenetic architecture affects proto-oncogene deregulation in cancer. We discuss how recently identified ecDNA functions may impact oncogenesis but also serve as new therapeutic vulnerabilities in cancer.
Topics: Humans; Oncogenes; Neoplasms; Chromosomes; DNA
PubMed: 35953594
DOI: 10.1038/s41576-022-00521-5 -
Cell Nov 2021RNA, DNA, and protein molecules are highly organized within three-dimensional (3D) structures in the nucleus. Although RNA has been proposed to play a role in nuclear...
RNA, DNA, and protein molecules are highly organized within three-dimensional (3D) structures in the nucleus. Although RNA has been proposed to play a role in nuclear organization, exploring this has been challenging because existing methods cannot measure higher-order RNA and DNA contacts within 3D structures. To address this, we developed RNA & DNA SPRITE (RD-SPRITE) to comprehensively map the spatial organization of RNA and DNA. These maps reveal higher-order RNA-chromatin structures associated with three major classes of nuclear function: RNA processing, heterochromatin assembly, and gene regulation. These data demonstrate that hundreds of ncRNAs form high-concentration territories throughout the nucleus, that specific RNAs are required to recruit various regulators into these territories, and that these RNAs can shape long-range DNA contacts, heterochromatin assembly, and gene expression. These results demonstrate a mechanism where RNAs form high-concentration territories, bind to diffusible regulators, and guide them into compartments to regulate essential nuclear functions.
Topics: Animals; Cell Nucleus; Chromobox Protein Homolog 5; Chromosomes; DNA; DNA, Satellite; DNA-Binding Proteins; Dactinomycin; Female; Genome; HEK293 Cells; Heterochromatin; Humans; Mice; Models, Biological; Multigene Family; RNA; RNA Polymerase II; RNA Processing, Post-Transcriptional; RNA Splicing; RNA, Long Noncoding; RNA, Messenger; RNA, Ribosomal; RNA-Binding Proteins; Transcription, Genetic
PubMed: 34739832
DOI: 10.1016/j.cell.2021.10.014 -
BMC Medicine Dec 2021During starvation, fasting, or a diet containing little digestible carbohydrates, the circulating insulin levels are decreased. This promotes lipolysis, and the... (Review)
Review
During starvation, fasting, or a diet containing little digestible carbohydrates, the circulating insulin levels are decreased. This promotes lipolysis, and the breakdown of fat becomes the major source of energy. The hepatic energy metabolism is regulated so that under these circumstances, ketone bodies are generated from β-oxidation of fatty acids and secreted as ancillary fuel, in addition to gluconeogenesis. Increased plasma levels of ketone bodies thus indicate a dietary shortage of carbohydrates. Ketone bodies not only serve as fuel but also promote resistance to oxidative and inflammatory stress, and there is a decrease in anabolic insulin-dependent energy expenditure. It has been suggested that the beneficial non-metabolic actions of ketone bodies on organ functions are mediated by them acting as a ligand to specific cellular targets. We propose here a major role of a different pathway initiated by the induction of oxidative stress in the mitochondria during increased ketolysis. Oxidative stress induced by ketone body metabolism is beneficial in the long term because it initiates an adaptive (hormetic) response characterized by the activation of the master regulators of cell-protective mechanism, nuclear factor erythroid 2-related factor 2 (Nrf2), sirtuins, and AMP-activated kinase. This results in resolving oxidative stress, by the upregulation of anti-oxidative and anti-inflammatory activities, improved mitochondrial function and growth, DNA repair, and autophagy. In the heart, the adaptive response to enhanced ketolysis improves resistance to damage after ischemic insults or to cardiotoxic actions of doxorubicin. Sodium-dependent glucose co-transporter 2 (SGLT2) inhibitors may also exert their cardioprotective action via increasing ketone body levels and ketolysis. We conclude that the increased synthesis and use of ketone bodies as ancillary fuel during periods of deficient food supply and low insulin levels causes oxidative stress in the mitochondria and that the latter initiates a protective (hormetic) response which allows cells to cope with increased oxidative stress and lower energy availability. KEYWORDS: Ketogenic diet, Ketone bodies, Beta hydroxybutyrate, Insulin, Obesity, Type 2 diabetes, Inflammation, Oxidative stress, Cardiovascular disease, SGLT2, Hormesis.
Topics: Diabetes Mellitus, Type 2; Energy Metabolism; Friends; Humans; Insulin; Ketone Bodies
PubMed: 34879839
DOI: 10.1186/s12916-021-02185-0 -
American Journal of Cancer Research 2021Liquid-liquid phase separation (LLPS) has emerged as a mechanism that has been used to explain the formation of known organelles (e.g. nucleoli, promyelocytic leukemia... (Review)
Review
Liquid-liquid phase separation (LLPS) has emerged as a mechanism that has been used to explain the formation of known organelles (e.g. nucleoli, promyelocytic leukemia nuclear bodies (PML NBs), etc) as well as other membraneless condensates (e.g. nucleosome arrays, DNA damage foci, X-chromosome inactivation (XCI) center, paraspeckles, stress granules, proteasomes, autophagosomes, etc). The formation of membraneless condensates could be triggered by proteins containing modular domains or intrinsically disordered regions (IDRs) and nucleic acids. Multiple biological processes including transcription, chromatin organization, X-chromosome inactivation (XCI), DNA damage, tumorigenesis, autophagy, etc have been shown to utilize the principle of LLPS to facilitate these processes. This review will summarize the principle and components of LLPS, and describe how LLPS regulate these numerous biological processes and disruption of LLPS would cause disease formation. The role of LLPS in regulating normal cellular physiology and contributing to tumorigenesis will be discussed.
PubMed: 34522448
DOI: No ID Found -
Nature May 2020Intracellular bodies such as nucleoli, Cajal bodies and various signalling assemblies represent membraneless organelles, or condensates, that form via liquid-liquid...
Intracellular bodies such as nucleoli, Cajal bodies and various signalling assemblies represent membraneless organelles, or condensates, that form via liquid-liquid phase separation (LLPS). Biomolecular interactions-particularly homotypic interactions mediated by self-associating intrinsically disordered protein regions-are thought to underlie the thermodynamic driving forces for LLPS, forming condensates that can facilitate the assembly and processing of biochemically active complexes, such as ribosomal subunits within the nucleolus. Simplified model systems have led to the concept that a single fixed saturation concentration is a defining feature of endogenous LLPS, and has been suggested as a mechanism for intracellular concentration buffering. However, the assumption of a fixed saturation concentration remains largely untested within living cells, in which the richly multicomponent nature of condensates could complicate this simple picture. Here we show that heterotypic multicomponent interactions dominate endogenous LLPS, and give rise to nucleoli and other condensates that do not exhibit a fixed saturation concentration. As the concentration of individual components is varied, their partition coefficients change in a manner that can be used to determine the thermodynamic free energies that underlie LLPS. We find that heterotypic interactions among protein and RNA components stabilize various archetypal intracellular condensates-including the nucleolus, Cajal bodies, stress granules and P-bodies-implying that the composition of condensates is finely tuned by the thermodynamics of the underlying biomolecular interaction network. In the context of RNA-processing condensates such as the nucleolus, this manifests in the selective exclusion of fully assembled ribonucleoprotein complexes, providing a thermodynamic basis for vectorial ribosomal RNA flux out of the nucleolus. This methodology is conceptually straightforward and readily implemented, and can be broadly used to extract thermodynamic parameters from microscopy images. These approaches pave the way for a deeper understanding of the thermodynamics of multicomponent intracellular phase behaviour and its interplay with the nonequilibrium activity that is characteristic of endogenous condensates.
Topics: Adaptor Proteins, Signal Transducing; Cell Nucleolus; Coiled Bodies; Cytoplasmic Granules; DNA Helicases; HeLa Cells; Humans; Intracellular Space; Nuclear Proteins; Nucleophosmin; Organelles; Phase Transition; Poly-ADP-Ribose Binding Proteins; RNA Helicases; RNA Recognition Motif Proteins; RNA, Ribosomal; RNA-Binding Proteins; Ribosomes; Thermodynamics
PubMed: 32405004
DOI: 10.1038/s41586-020-2256-2 -
RNA (New York, N.Y.) Jan 2022Macroscopic membraneless organelles containing RNA such as the nucleoli, germ granules, and the Cajal body have been known for decades. These biomolecular condensates... (Review)
Review
Macroscopic membraneless organelles containing RNA such as the nucleoli, germ granules, and the Cajal body have been known for decades. These biomolecular condensates are liquid-like bodies that can be formed by a phase transition. Recent evidence has revealed the presence of similar microscopic condensates associated with the transcription of genes. This brief article summarizes thoughts about the importance of condensates in the regulation of transcription and how RNA molecules, as components of such condensates, control the synthesis of RNA. Models and experimental data suggest that RNAs from enhancers facilitate the formation of a condensate that stabilizes the binding of transcription factors and accounts for a burst of transcription at the promoter. Termination of this burst is pictured as a nonequilibrium feedback loop where additional RNA destabilizes the condensate.
Topics: Binding Sites; Biomolecular Condensates; Cell Compartmentation; Cell Nucleolus; Coiled Bodies; DNA; Eukaryotic Cells; Feedback, Physiological; Germ Cell Ribonucleoprotein Granules; Humans; Macromolecular Substances; Promoter Regions, Genetic; Protein Binding; RNA; RNA-Binding Proteins; Transcription Factors; Transcription, Genetic
PubMed: 34772787
DOI: 10.1261/rna.078997.121 -
Cells Oct 2021Small ubiquitin-related modifier (SUMO) is a member of the ubiquitin-related protein family. SUMO modulates protein function through covalent conjugation to lysine... (Review)
Review
Small ubiquitin-related modifier (SUMO) is a member of the ubiquitin-related protein family. SUMO modulates protein function through covalent conjugation to lysine residues in a large number of proteins. Once covalently conjugated to a protein, SUMO often regulates that protein's function by recruiting other cellular proteins. Recruitment frequently involves a non-covalent interaction between SUMO and a SUMO-interacting motif (SIM) in the interacting protein. SIMs generally consist of a four-residue-long hydrophobic stretch of amino acids with aliphatic non-polar side chains flanked on one side by negatively charged amino acid residues. The SIM assumes an extended β-strand-like conformation and binds to a conserved hydrophobic groove in SUMO. In addition to hydrophobic interactions between the SIM non-polar core and hydrophobic residues in the groove, the negatively charged residues in the SIM make favorable electrostatic contacts with positively charged residues in and around the groove. The SIM/SUMO interaction can be regulated by the phosphorylation of residues adjacent to the SIM hydrophobic core, which provide additional negative charges for favorable electrostatic interaction with SUMO. The SUMO interactome consists of hundreds or perhaps thousands of SIM-containing proteins, but we do not fully understand how each SUMOylated protein selects the set of SIM-containing proteins appropriate to its function. SIM/SUMO interactions have critical functions in a large number of essential cellular processes including the formation of membraneless organelles by liquid-liquid phase separation, epigenetic regulation of transcription through histone modification, DNA repair, and a variety of host-pathogen interactions.
Topics: Amino Acid Motifs; Amino Acid Sequence; Animals; DNA Breaks, Double-Stranded; DNA Repair; Histones; Humans; Promyelocytic Leukemia Nuclear Bodies; Protein Interaction Mapping; Small Ubiquitin-Related Modifier Proteins
PubMed: 34831049
DOI: 10.3390/cells10112825 -
Cold Spring Harbor Perspectives in... Aug 2021Viral infection is intrinsically linked to the capacity of the virus to generate progeny. Many DNA and some RNA viruses need to access the nuclear machinery and... (Review)
Review
Viral infection is intrinsically linked to the capacity of the virus to generate progeny. Many DNA and some RNA viruses need to access the nuclear machinery and therefore transverse the nuclear envelope barrier through the nuclear pore complex. Viral genomes then become chromatinized either in their episomal form or upon integration into the host genome. Interactions with host DNA, transcription factors or nuclear bodies mediate their replication. Often interfering with nuclear functions, viruses use nuclear architecture to ensure persistent infections. Discovering these multiple modes of replication and persistence served in unraveling many important nuclear processes, such as nuclear trafficking, transcription, and splicing. Here, by using examples of DNA and RNA viral families, we portray the nucleus with the virus inside.
Topics: Animals; Cell Nucleus; DNA Viruses; Gene Expression Regulation, Viral; Humans; RNA Viruses; Virus Integration
PubMed: 33753405
DOI: 10.1101/cshperspect.a039446 -
Nature Communications Apr 2023Cellular senescence contributes to tissue homeostasis and age-related pathologies. However, how senescence is initiated in stressed cells remains vague. Here, we...
Cellular senescence contributes to tissue homeostasis and age-related pathologies. However, how senescence is initiated in stressed cells remains vague. Here, we discover that exposure to irradiation, oxidative or inflammatory stressors induces transient biogenesis of primary cilia, which are then used by stressed cells to communicate with the promyelocytic leukemia nuclear bodies (PML-NBs) to initiate senescence responses in human cells. Mechanistically, a ciliary ARL13B-ARL3 GTPase cascade negatively regulates the association of transition fiber protein FBF1 and SUMO-conjugating enzyme UBC9. Irreparable stresses downregulate the ciliary ARLs and release UBC9 to SUMOylate FBF1 at the ciliary base. SUMOylated FBF1 then translocates to PML-NBs to promote PML-NB biogenesis and PML-NB-dependent senescence initiation. Remarkably, Fbf1 ablation effectively subdues global senescence burden and prevents associated health decline in irradiation-treated mice. Collectively, our findings assign the primary cilium a key role in senescence induction in mammalian cells and, also, a promising target in future senotherapy strategies.
Topics: Humans; Animals; Mice; Promyelocytic Leukemia Protein; Nuclear Proteins; Cilia; Promyelocytic Leukemia Nuclear Bodies; Sumoylation; Cell Nucleus; Mammals; Adaptor Proteins, Signal Transducing
PubMed: 37019904
DOI: 10.1038/s41467-023-37362-7