| 51. |
- Lehmann, Laura C., et al.
(författare)
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Mechanistic Insights into Autoinhibition of the Oncogenic Chromatin Remodeler ALC1
- 2017
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 68:5, s. 847-859 (e7)
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Tidskriftsartikel (refereegranskat)abstract
- Human ALC1 is an oncogene-encoded chromatin-remodeling enzyme required for DNA repair that possesses a poly(ADP-ribose) (PAR)-binding macro domain. Its engagement with PARylated PARP1 activates ALC1 at sites of DNA damage, but the underlying-mechanism remains unclear. Here, we establish a dual role for the macro domain in autoinhibition of ALC1 ATPase activity and coupling to nucleosome mobilization. In the absence of DNA damage, an inactive conformation of the ATPase is maintained by juxtaposition of the macro domain against predominantly the C-terminal ATPase lobe through conserved electrostatic interactions. Mutations within this interface displace the macro domain, constitutively activate the ALC1 ATPase independent of PARylated PARP1, and alter the dynamics of ALC1 recruitment at DNA damage sites. Upon DNA damage, binding of PARylated PARP1 by the macro domain induces a conformational change that relieves autoinhibitory interactions with the ATPase motor, which selectively activates ALC1 remodeling upon recruitment to sites of DNA damage.
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| 52. |
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| 53. |
- Levine, Daniel C., et al.
(författare)
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NAD+ Controls Circadian Reprogramming through PER2 Nuclear Translocation to Counter Aging
- 2020
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 78:5, s. 835-
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Tidskriftsartikel (refereegranskat)abstract
- Disrupted sleep-wake and molecular circadian rhythms are a feature of aging associated with metabolic disease and reduced levels of NAD(+), yet whether changes in nucleotide metabolism control circadian behavioral and genomic rhythms remains unknown. Here, we reveal that supplementation with the NAD(+) precursor nicotinamide riboside (NR) markedly reprograms metabolic and stress-response pathways that decline with aging through inhibition of the clock repressor PER2. NR enhances BMAL1 chromatin binding genome-wide through PER2K680 deacetylation, which in turn primes PER2 phosphorylation within a domain that controls nuclear transport and stability and that is mutated in human advanced sleep phase syndrome. In old mice, dampened BMAL1 chromatin binding, transcriptional oscillations, mitochondrial respiration rhythms, and late evening activity are restored by NAD(+) repletion to youthful levels with NR. These results reveal effects of NAD(+) on metabolism and the circadian system with aging through the spatiotemporal control of the molecular clock.
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| 54. |
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| 55. |
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| 56. |
- Luengo, Alba, et al.
(författare)
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Increased demand for NAD + relative to ATP drives aerobic glycolysis
- 2021
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-4164 .- 1097-2765. ; 81:4, s. 691-707.e6
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Tidskriftsartikel (refereegranskat)abstract
- Aerobic glycolysis, or preferential fermentation of glucose-derived pyruvate to lactate despite available oxygen, is associated with proliferation across many organisms and conditions. To better understand that association, we examined the metabolic consequence of activating the pyruvate dehydrogenase complex (PDH) to increase pyruvate oxidation at the expense of fermentation. We find that increasing PDH activity impairs cell proliferation by reducing the NAD+/NADH ratio. This change in NAD+/NADH is caused by increased mitochondrial membrane potential that impairs mitochondrial electron transport and NAD+ regeneration. Uncoupling respiration from ATP synthesis or increasing ATP hydrolysis restores NAD+/NADH homeostasis and proliferation even when glucose oxidation is increased. These data suggest that when demand for NAD+ to support oxidation reactions exceeds the rate of ATP turnover in cells, NAD+ regeneration by mitochondrial respiration becomes constrained, promoting fermentation, despite available oxygen. This argues that cells engage in aerobic glycolysis when the demand for NAD+ is in excess of the demand for ATP. Aerobic glycolysis is associated with proliferation in many biological contexts, yet what drives this phenotype has not been fully explained. Luengo et al. show that cells engage in aerobic glycolysis when the demand for NAD+ exceeds the demand for ATP, which leads to impaired NAD+ regeneration by mitochondrial respiration.
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| 57. |
- Lönn, Peter, et al.
(författare)
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PARP-1 attenuates Smad-mediated transcription
- 2010
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-2765 .- 1097-4164. ; 40:4, s. 521-532
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Tidskriftsartikel (refereegranskat)abstract
- The versatile cytokine transforming growth factor β (TGF-β) regulates cellular growth, differentiation, and migration during embryonic development and adult tissue homeostasis. Activation of TGF-β receptors leads to phosphorylation of Smad2 and Smad3, which oligomerize with Smad4 and accumulate in the nucleus where they recognize gene regulatory regions and orchestrate transcription. Termination of Smad-activated transcription involves Smad dephosphorylation, nuclear export, or ubiquitin-mediated degradation. In an unbiased proteomic screen, we identified poly(ADP-ribose) polymerase-1 (PARP-1) as a Smad-interacting partner. PARP-1 dissociates Smad complexes from DNA by ADP-ribosylating Smad3 and Smad4, which attenuates Smad-specific gene responses and TGF-β-induced epithelial-mesenchymal transition. Thus, our results identify ADP-ribosylation of Smad proteins by PARP-1 as a key step in controlling the strength and duration of Smad-mediated transcription.
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| 58. |
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| 59. |
- Mestdagh, Pieter, et al.
(författare)
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The miR-17-92 MicroRNA Cluster Regulates Multiple Components of the TGF-beta Pathway in Neuroblastoma
- 2010
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Ingår i: Molecular Cell. - : Elsevier BV. - 1097-4164 .- 1097-2765. ; 40:5, s. 762-773
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Tidskriftsartikel (refereegranskat)abstract
- The miR-17-92 microRNA cluster is often activated in cancer cells, but the identity of its targets remains elusive. Using SILAC and quantitative mass spectrometry, we examined the effects of activation of the miR-17-92 cluster on global protein expression in neuroblastoma (NB) cells. Our results reveal cooperation between individual miR-17-92 miRNAs and implicate miR-17-92 in multiple hallmarks of cancer, including proliferation and cell adhesion. Most importantly, we show that miR-17-92 is a potent inhibitor of TGF-beta signaling. By functioning both upstream and downstream of pSMAD2, miR-17-92 activation triggers downregulation of multiple key effectors along the TGF-beta signaling cascade as well as direct inhibition of TGF-beta-responsive genes.
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| 60. |
- Meydan, Sezen, et al.
(författare)
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Retapamulin-Assisted Ribosome Profiling Reveals the Alternative Bacterial Proteome
- 2019
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Ingår i: Molecular Cell. - : Elsevier. - 1097-2765 .- 1097-4164. ; 74:3, s. 481-
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Tidskriftsartikel (refereegranskat)abstract
- The use of alternative translation initiation sites enables production of more than one protein from a single gene, thereby expanding the cellular proteome. Although several such examples have been serendipitously found in bacteria, genome-wide mapping of alternative translation start sites has been unattainable. We found that the antibiotic retapamulin specifically arrests initiating ribosomes at start codons of the genes. Retapamulin-enhanced Ribo-seq analysis (Ribo-RET) not only allowed mapping of conventional initiation sites at the beginning of the genes, but strikingly, it also revealed putative internal start sites in a number of Escherichia coli genes. Experiments demonstrated that the internal start codons can be recognized by the ribosomes and direct translation initiation in vitro and in vivo. Proteins, whose synthesis is initiated at internal in-frame and out-of-frame start sites, can be functionally important and contribute to the "alternative" bacterial proteome. The internal start sites may also play regulatory roles in gene expression.
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