Single-nucleoid architecture reveals heterogeneous packaging of mitochondrial DNA [RNA-seq]
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE240902 | GEO | 2023/11/15
REPOSITORIES: GEO
Similar Datasets
Project description:Cellular metabolism relies on the regulation and maintenance of mitochondrial DNA (mtDNA). Hundreds to thousands of copies of mtDNA exist in each cell, yet because mitochondria lack histones or other machinery important for nuclear genome compaction, it remains unresolved how mtDNA is packaged into individual nucleoids. In this study, we used long-read single-molecule accessibility mapping to measure the compaction of individual full-length mtDNA molecules at near single-nucleotide resolution. We found that, unlike the nuclear genome, human mtDNA largely undergoes all-or-none global compaction, with most nucleoids existing in an inaccessible, inactive state. Highly accessible mitochondrial nucleoids are co-occupied by transcription and replication components and selectively form a triple-stranded displacement loop structure. In addition, we showed that the primary nucleoid-associated protein TFAM directly modulates the fraction of inaccessible nucleoids both in vivo and in vitro, acting consistently with a nucleation-and-spreading mechanism to coat and compact mitochondrial nucleoids. Together, these findings reveal the primary architecture of mtDNA packaging and regulation in human cells.
2023-11-13 | GSE212611 | GEO
Project description:Cellular metabolism relies on the regulation and maintenance of mitochondrial DNA (mtDNA). Hundreds to thousands of copies of mtDNA exist in each cell, yet because mitochondria lack histones or other machinery important for nuclear genome compaction, it remains unresolved how mtDNA is packaged into individual nucleoids. In this study, we used long-read single-molecule accessibility mapping to measure the compaction of individual full-length mtDNA molecules at near single-nucleotide resolution. We found that, unlike the nuclear genome, human mtDNA largely undergoes all-or-none global compaction, with most nucleoids existing in an inaccessible, inactive state. Highly accessible mitochondrial nucleoids are co-occupied by transcription and replication components and selectively form a triple-stranded displacement loop structure. In addition, we showed that the primary nucleoid-associated protein TFAM directly modulates the fraction of inaccessible nucleoids both in vivo and in vitro, acting consistently with a nucleation-and-spreading mechanism to coat and compact mitochondrial nucleoids. Together, these findings reveal the primary architecture of mtDNA packaging and regulation in human cells.
2023-11-15 | GSE212608 | GEO
Project description:Cellular metabolism relies on the regulation and maintenance of mitochondrial DNA (mtDNA). Hundreds to thousands of copies of mtDNA exist in each cell, yet because mitochondria lack histones or other machinery important for nuclear genome compaction, it remains unresolved how mtDNA is packaged into individual nucleoids. In this study, we used long-read single-molecule accessibility mapping to measure the compaction of individual full-length mtDNA molecules at near single-nucleotide resolution. We found that, unlike the nuclear genome, human mtDNA largely undergoes all-or-none global compaction, with most nucleoids existing in an inaccessible, inactive state. Highly accessible mitochondrial nucleoids are co-occupied by transcription and replication components and selectively form a triple-stranded displacement loop structure. In addition, we showed that the primary nucleoid-associated protein TFAM directly modulates the fraction of inaccessible nucleoids both in vivo and in vitro, acting consistently with a nucleation-and-spreading mechanism to coat and compact mitochondrial nucleoids. Together, these findings reveal the primary architecture of mtDNA packaging and regulation in human cells.
2023-11-15 | GSE212600 | GEO
Project description:Autoantibodies against nucleic acids and excessive type I Interferon (IFN) are hallmarks of human Systemic Lupus Erythematosus (SLE). We previously reported that SLE neutrophils, exposed to TLR7-agonist autoantibodies, release interferogenic DNA, which we now demonstrate to be of mitochondrial origin. We further show that healthy human neutrophils do not complete mitophagy upon induction of mitochondrial damage. Rather, they extrude mitochondrial components, including DNA (mtDNA), devoid of oxidized residues. When MtDNA undergoes oxidation, it is directly routed to lysosomes for degradation. This rerouting requires dissociation from the transcription factor TFAM, a dual high mobility group (HMG) protein involved in maintenance and compaction of the mitochondrial genome into nucleoids. Exposure of SLE neutrophils, or healthy IFNprimed neutrophils, to anti-RNP autoantibodies blocks TFAM phosphorylation, a necessary step for nucleoid dissociation. Consequently, oxidized nucleoids accumulate within mitochondria and are eventually extruded as potent interferogenic complexes. In support of the in vivo relevance of this phenomenon, mitochondrial retention of oxidized nucleoids is a feature of SLE blood neutrophils, and autoantibodies against oxidized mtDNA are present in a fraction of patients. This pathway represents a novel therapeutic target in human SLE. 4 samples, no replicates, 2 controls. 2 samples are Neutrophils cultured with and without CCCP (control). 2 samples are Monocytes cultured with and without CCCP (control).
2016-04-07 | E-GEOD-78243 | biostudies-arrayexpress
Project description:Autoantibodies against nucleic acids and excessive type I Interferon (IFN) are hallmarks of human Systemic Lupus Erythematosus (SLE). We previously reported that SLE neutrophils, exposed to TLR7-agonist autoantibodies, release interferogenic DNA, which we now demonstrate to be of mitochondrial origin. We further show that healthy human neutrophils do not complete mitophagy upon induction of mitochondrial damage. Rather, they extrude mitochondrial components, including DNA (mtDNA), devoid of oxidized residues. When MtDNA undergoes oxidation, it is directly routed to lysosomes for degradation. This rerouting requires dissociation from the transcription factor TFAM, a dual high mobility group (HMG) protein involved in maintenance and compaction of the mitochondrial genome into nucleoids. Exposure of SLE neutrophils, or healthy IFNprimed neutrophils, to anti-RNP autoantibodies blocks TFAM phosphorylation, a necessary step for nucleoid dissociation. Consequently, oxidized nucleoids accumulate within mitochondria and are eventually extruded as potent interferogenic complexes. In support of the in vivo relevance of this phenomenon, mitochondrial retention of oxidized nucleoids is a feature of SLE blood neutrophils, and autoantibodies against oxidized mtDNA are present in a fraction of patients. This pathway represents a novel therapeutic target in human SLE.
2016-04-07 | GSE78243 | GEO
Project description:Mitochondrial DNA (mtDNA) breaks are deleterious lesions that lead to degradation of mitochondrial genomes and subsequent reduction in mtDNA copy number. The signaling pathways activated in response to mtDNA damage remain ill-defined. Using mitochondrial targeted restriction enzymes, we show that cells with mtDNA breaks exhibit reduced respiratory complexes, loss of membrane potential, and mitochondrial protein import defect. Furthermore, mtDNA damage activates the integrated stress response (ISR) through phosphorylation of eIF2α by the OMA1-DELE1-HRI pathway. Electron microscopy reveals concomitant defects in mitochondrial membranes and cristae ultrastructure. Notably, inhibition of the ISR exacerbates mitochondrial defects and delays the recovery of mtDNA copy number, thereby implicating this stress response in mitigating mitochondrial dysfunction following mtDNA damage. Last, we provide evidence suggesting that ATAD3A, a membrane-anchored protein that interacts with nucleoids, relays the signal from mtDNA breaks to the inner mitochondrial membrane. Altogether, our study fully delineates the sequence of events linking damaged mitochondrial genomes with the cytoplasm and uncovers an unanticipated role for the ISR in response to mitochondrial genome instability.
2022-10-04 | GSE214512 | GEO
Project description:Mitochondrial DNA (mtDNA) breaks are toxic lesions that lead to degradation of mitochondrial genomes and subsequent reduction in mtDNA copy number. The signaling pathways activated in response to mtDNA damage remain poorly understood. We reasoned that factors that sense mtDNA damage are likely to be recruited to nucleoids shortly after break formation, prompting us to develop a proteomic-based approach to survey the interactome of mitochondrial nucleoids. Specifically, we combined proximity-dependent biotin labeling with Stable Isotope Labeling by Amino acids in Cell culture (SILAC) and tandem mass spectrometry. We used mitochondrial targeted restriction enzymes for the proximity probe and show that cells with mtDNA breaks exhibit reduced respiratory complexes, loss of membrane potential, and mitochondrial protein import defect. Notably, mtDNA breaks activate the integrated stress response (ISR) through phosphorylation of eIF2a by the OMA1-DELE1-HRI pathway. Inhibition of the ISR exacerbates mitochondrial defects and delays the recovery of mtDNA copy number, hinting at a role for the ISR in mitigating mitochondrial dysfunction following mtDNA damage. Electron microscopy reveals defective mitochondrial membranes and cristae ultrastructure. Last, we highlight a potential role for ATAD3A - a protein that is anchored to the inner mitochondrial membrane while interacting with nucleoids - in relaying the signal from damaged mtDNA to the mitochondrial inner membrane. Altogether, our study delineates the sequence of events linking damaged mitochondrial genomes to the cytoplasmic stress response. The mass spectrometry raw files for the combined SILAC and proximity-dependent biotin labeling experiment are deposited here.
2022-10-05 | MSV000090459 | MassIVE
Project description:<p> Human disorders of mitochondrial oxidative phosphorylation (OXPHOS) represent a devastating collection of inherited diseases. These disorders impact at least 1:5000 live births, and are characterized by multi-organ system involvement. They are characterized by remarkable locus heterogeneity, with mutations in the mtDNA as well as in over 77 nuclear genes identified to date. It is estimated that additional genes may be mutated in these disorders. </p> <p>To discover the genetic causes of mitochondrial OXPHOS diseases, we performed targeted, deep sequencing of the entire mitochondrial genome (mtDNA) and the coding exons of over 1000 nuclear genes encoding the mitochondrial proteome. We applied this 'MitoExome' sequencing to 124 unrelated patients with a wide range of OXPHOS disease presentations from the Massachusetts General Hospital Mitochondrial Disorders Clinic. </p> <p>The 2.3Mb targeted region was captured by hybrid selection and Illumina sequenced with paired 76bp reads. The total set of 1605 targeted nuclear genes included 1013 genes with strong evidence of mitochondrial localization from the MitoCarta database, 377 genes with weaker evidence of mitochondrial localization from the MitoP2 database and other sources, and 215 genes known to cause other inborn errors of metabolism. Approximately 88% of targeted bases were well-covered (>20X), with mean 200X coverage per targeted base. </p>
| phs000339 | dbGaP
Project description:Integrity of mitochondrial DNA (mtDNA), encoding several subunits of the respiratory chain, is essential to maintain mitochondrial fitness. Mitochondria, as a central hub for metabolism, are affected in a wide variety of human diseases but also during normal ageing, where mtDNA integrity is compromised. Mitochondrial quality control mechanisms work at different levels, and mitophagy and its variants are critical to remove dysfunctional mitochondria and mtDNA to maintain cellular homeostasis. Understanding the mechanisms governing a selective turnover of mutation-bearing mtDNA without affecting the entire mitochondrial pool is fundamental to design therapeutic strategies against mtDNA diseases and ageing. Here, we show that mtDNA damage after expressing a dominant negative version of the mitochondrial helicase Twinkle, or by chemical means, leads to an exacerbated mtDNA turnover. mtDNA removal depends on lysosomal function and requires the autophagy protein Atg5 but is independent of canonical mitophagy or autophagy. Using proximity labelling, we demonstrated that the area of influence of mitochondrial nucleoids differs upon mtDNA damage, which induces mitochondrial membrane remodelling and endosomal recruitment in close proximity to mitochondrial nucleoid sub compartments. Targeting of nucleoids is controlled by the mitochondrial transmembrane proteins ATAD3 and SAMM50, which together with the endosomal trafficking protein VPS35, orchestrate endosomal nucleoid engulfment. SAMM50 acts as a gatekeeper to avoid mtDNA release to the cytoplasm and facilitating mtDNA transfer to VPS35. Lastly, we show that stimulation of lysosomal activity by rapamycin selectively removes mtDNA deletions in vivo, without affecting mtDNA copy number. With these results, we unveil the molecular players of a new complex mechanism specifically targeting and removing mutant mtDNA which occurs outside the mitochondrial network, a process with multiple potential benefits to understand human mtDNA related diseases, either inherited, acquired or due to normal ageing.
2022-11-07 | PXD023939 | Pride
Project description:Mammalian mitochondrial DNA (mtDNA) is coated with mitochondrial transcription factor A (TFAM) and compacted into nucleoids. TFAM is not only the main component of mitochondrial nucleoids but its levels can also control mtDNA copy number. Here we show that the TFAM-to-mtDNA ratio is critical for maintaining normal mtDNA expression in different tissues of the mouse. BAC transgenic mice with a 1.5-fold increase in TFAM protein levels maintain a normal TFAM-to-mtDNA ratio in different tissues and as a consequence mitochondrial gene expression, nucleoid distribution and whole animal metabolism are all unaltered. In contrast, mice expressing TFAM from the CAG promoter in the ROSA26 locus have 4.5-fold increase of TFAM protein levels in heart and skeletal muscle and develop pathology leading to early postnatal lethality. The TFAM-to-mtDNA ratio varies widely between tissues in these mice and is very high in skeletal muscle where it causes strong repression of mtDNA expression and deficient oxidative phosphorylation (OXPHOS) despite normal mtDNA levels. In heart, mtDNA copy number is increased leading to a near normal TFAM-to-mtDNA ratio and maintained OXPHOS capacity. In the liver, mtDNA expression is maintained despite increased TFAM levels and normal mtDNA levels. Here, tissue-specific induction of the LONP1 protease and mitochondrial RNA polymerase (POLRMT) expression counteracts the silencing effect of high TFAM levels. We conclude that the TFAM-to-mtDNA ratio has an important role in maintaining mtDNA expression in vivo. TFAM acts as a general repressor of mtDNA expression and this effect can be counterbalance by tissue-specific expression of regulatory factors.
2021-08-18 | PXD023050 | Pride