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Molecular Cell

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https://www.readbyqxmd.com/read/28216227/nek7-protects-telomeres-from-oxidative-dna-damage-by-phosphorylation-and-stabilization-of-trf1
#1
Rong Tan, Satoshi Nakajima, Qun Wang, Hongxiang Sun, Jing Xue, Jian Wu, Sabine Hellwig, Xuemei Zeng, Nathan A Yates, Thomas E Smithgall, Ming Lei, Yu Jiang, Arthur S Levine, Bing Su, Li Lan
Telomeric repeat binding factor 1 (TRF1) is essential to the maintenance of telomere chromatin structure and integrity. However, how telomere integrity is maintained, especially in response to damage, remains poorly understood. Here, we identify Nek7, a member of the Never in Mitosis Gene A (NIMA) kinase family, as a regulator of telomere integrity. Nek7 is recruited to telomeres and stabilizes TRF1 at telomeres after damage in an ATM activation-dependent manner. Nek7 deficiency leads to telomere aberrations, long-lasting γH2AX and 53BP1 foci, and augmented cell death upon oxidative telomeric DNA damage...
February 8, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28216226/nbs1-phosphorylation-status-dictates-repair-choice-of-dysfunctional-telomeres
#2
Rekha Rai, Chunyi Hu, Cayla Broton, Yong Chen, Ming Lei, Sandy Chang
Telomeres employ TRF2 to protect chromosome ends from activating the DNA damage sensor MRE11-RAD50-NBS1 (MRN), thereby repressing ATM-dependent DNA damage checkpoint responses. How TRF2 prevents MRN activation at dysfunctional telomeres is unclear. Here, we show that the phosphorylation status of NBS1 determines the repair pathway choice of dysfunctional telomeres. The crystal structure of the TRF2-NBS1 complex at 3.0 Å resolution shows that the NBS1 429YQLSP433 motif interacts specifically with the TRF2(TRFH) domain...
February 8, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28190768/serine-adp-ribosylation-depends-on-hpf1
#3
Juan José Bonfiglio, Pietro Fontana, Qi Zhang, Thomas Colby, Ian Gibbs-Seymour, Ilian Atanassov, Edward Bartlett, Roko Zaja, Ivan Ahel, Ivan Matic
ADP-ribosylation (ADPr) regulates important patho-physiological processes through its attachment to different amino acids in proteins. Recently, by precision mapping on all possible amino acid residues, we identified histone serine ADPr marks in the DNA damage response. However, the biochemical basis underlying this serine modification remained unknown. Here we report that serine ADPr is strictly dependent on histone PARylation factor 1 (HPF1), a recently identified regulator of PARP-1. Quantitative proteomics revealed that serine ADPr does not occur in cells lacking HPF1...
February 8, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28190770/nuclear-rna-decay-pathways-aid-rapid-remodeling-of-gene-expression-in-yeast
#4
Stefan Bresson, Alex Tuck, Desislava Staneva, David Tollervey
In budding yeast, the nuclear RNA surveillance system is active on all pre-mRNA transcripts and modulated by nutrient availability. To test the role of nuclear surveillance in reprogramming gene expression, we identified transcriptome-wide binding sites for RNA polymerase II and the exosome cofactors Mtr4 (TRAMP complex) and Nab3 (NNS complex) by UV crosslinking immediately following glucose withdrawal (0, 4, and 8 min). In glucose, mRNA binding by Nab3 and Mtr4 was mainly restricted to promoter-proximal sites, reflecting early transcription termination...
January 27, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28190767/an-interaction-landscape-of-ubiquitin-signaling
#5
Xiaofei Zhang, Arne H Smits, Gabrielle B A van Tilburg, Pascal W T C Jansen, Matthew M Makowski, Huib Ovaa, Michiel Vermeulen
Intracellular signaling via the covalent attachment of different ubiquitin linkages to protein substrates is fundamental to many cellular processes. Although linkage-selective ubiquitin interactors have been studied on a case-by-case basis, proteome-wide analyses have not been conducted yet. Here, we present ubiquitin interactor affinity enrichment-mass spectrometry (UbIA-MS), a quantitative interaction proteomics method that makes use of chemically synthesized diubiquitin to enrich and identify ubiquitin linkage interactors from crude cell lysates...
January 25, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28132842/dna-double-strand-break-resection-occurs-during-non-homologous-end-joining-in-g1-but-is-distinct-from-resection-during-homologous-recombination
#6
Ronja Biehs, Monika Steinlage, Olivia Barton, Szilvia Juhász, Julia Künzel, Julian Spies, Atsushi Shibata, Penny A Jeggo, Markus Löbrich
Canonical non-homologous end joining (c-NHEJ) repairs DNA double-strand breaks (DSBs) in G1 cells with biphasic kinetics. We show that DSBs repaired with slow kinetics, including those localizing to heterochromatic regions or harboring additional lesions at the DSB site, undergo resection prior to repair by c-NHEJ and not alt-NHEJ. Resection-dependent c-NHEJ represents an inducible process during which Plk3 phosphorylates CtIP, mediating its interaction with Brca1 and promoting the initiation of resection. Mre11 exonuclease, EXD2, and Exo1 execute resection, and Artemis endonuclease functions to complete the process...
January 25, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28132844/active-interaction-mapping-reveals-the-hierarchical-organization-of-autophagy
#7
Michael H Kramer, Jean-Claude Farré, Koyel Mitra, Michael Ku Yu, Keiichiro Ono, Barry Demchak, Katherine Licon, Mitchell Flagg, Rama Balakrishnan, J Michael Cherry, Suresh Subramani, Trey Ideker
We have developed a general progressive procedure, Active Interaction Mapping, to guide assembly of the hierarchy of functions encoding any biological system. Using this process, we assemble an ontology of functions comprising autophagy, a central recycling process implicated in numerous diseases. A first-generation model, built from existing gene networks in Saccharomyces, captures most known autophagy components in broad relation to vesicle transport, cell cycle, and stress response. Systematic analysis identifies synthetic-lethal interactions as most informative for further experiments; consequently, we saturate the model with 156,364 such measurements across autophagy-activating conditions...
January 23, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28065598/cas13b-is-a-type-vi-b-crispr-associated-rna-guided-rnase-differentially-regulated-by-accessory-proteins-csx27-and-csx28
#8
Aaron A Smargon, David B T Cox, Neena K Pyzocha, Kaijie Zheng, Ian M Slaymaker, Jonathan S Gootenberg, Omar A Abudayyeh, Patrick Essletzbichler, Sergey Shmakov, Kira S Makarova, Eugene V Koonin, Feng Zhang
CRISPR-Cas adaptive immune systems defend microbes against foreign nucleic acids via RNA-guided endonucleases. Using a computational sequence database mining approach, we identify two class 2 CRISPR-Cas systems (subtype VI-B) that lack Cas1 and Cas2 and encompass a single large effector protein, Cas13b, along with one of two previously uncharacterized associated proteins, Csx27 and Csx28. We establish that these CRISPR-Cas systems can achieve RNA interference when heterologously expressed. Through a combination of biochemical and genetic experiments, we show that Cas13b processes its own CRISPR array with short and long direct repeats, cleaves target RNA, and exhibits collateral RNase activity...
January 4, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28065601/initiation-of-quality-control-during-poly-a-translation-requires-site-specific-ribosome-ubiquitination
#9
Szymon Juszkiewicz, Ramanujan S Hegde
Diverse cellular stressors have been observed to trigger site-specific ubiquitination on several ribosomal proteins. However, the ubiquitin ligases, biochemical consequences, and physiologic pathways linked to these modifications are not known. Here, we show in mammalian cells that the ubiquitin ligase ZNF598 is required for ribosomes to terminally stall during translation of poly(A) sequences. ZNF598-mediated stalling initiated the ribosome-associated quality control (RQC) pathway for degradation of nascent truncated proteins...
December 22, 2016: Molecular Cell
https://www.readbyqxmd.com/read/28212753/the-trail-induced-cancer-secretome-promotes-a-tumor-supportive-immune-microenvironment-via-ccr2
#10
Torsten Hartwig, Antonella Montinaro, Silvia von Karstedt, Alexandra Sevko, Silvia Surinova, Ankur Chakravarthy, Lucia Taraborrelli, Peter Draber, Elodie Lafont, Frederick Arce Vargas, Mona A El-Bahrawy, Sergio A Quezada, Henning Walczak
Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is known for specifically killing cancer cells, whereas in resistant cancers, TRAIL/TRAIL-R can promote metastasis via Rac1 and PI3K. It remains unknown, however, whether and to what extent TRAIL/TRAIL-R signaling in cancer cells can affect the immune microenvironment. Here we show that TRAIL-triggered cytokine secretion from TRAIL-resistant cancer cells is FADD dependent and identify the TRAIL-induced secretome to drive monocyte polarization to myeloid-derived suppressor cells (MDSCs) and M2-like macrophages...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212752/caspase-8-acts-in-a-non-enzymatic-role-as-a-scaffold-for-assembly-of-a-pro-inflammatory-faddosome-complex-upon-trail-stimulation
#11
Conor M Henry, Seamus J Martin
TRAIL is a potent inducer of apoptosis and has been studied almost exclusively in this context. However, TRAIL can also induce NFκB-dependent expression of multiple pro-inflammatory cytokines and chemokines. Surprisingly, whereas inhibition of caspase activity blocked TRAIL-induced apoptosis, but not cytokine production, knock down or deletion of caspase-8 suppressed both outcomes, suggesting that caspase-8 participates in TRAIL-induced inflammatory signaling in a scaffold role. Consistent with this, introduction of a catalytically inactive caspase-8 mutant into CASP-8 null cells restored TRAIL-induced cytokine production, but not cell death...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212751/stable-heritable-germline-silencing-directs-somatic-silencing-at-an-endogenous-locus
#12
Olga Minkina, Craig P Hunter
The importance of transgenerationally inherited epigenetic states to organismal fitness remains unknown as well-documented examples are often not amenable to mechanistic analysis or rely on artificial reporter loci. Here we describe an induced silenced state at an endogenous locus that persists, at 100% transmission without selection, for up to 13 generations. This unusually persistent silencing enables a detailed molecular genetic analysis of an inherited epigenetic state. We find that silencing is dependent on germline nuclear RNAi factors and post-transcriptional mechanisms...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212750/conformational-rigidity-and-protein-dynamics-at-distinct-timescales-regulate-ptp1b-activity-and-allostery
#13
Meng S Choy, Yang Li, Luciana E S F Machado, Micha B A Kunze, Christopher R Connors, Xingyu Wei, Kresten Lindorff-Larsen, Rebecca Page, Wolfgang Peti
Protein function originates from a cooperation of structural rigidity, dynamics at different timescales, and allostery. However, how these three pillars of protein function are integrated is still only poorly understood. Here we show how these pillars are connected in Protein Tyrosine Phosphatase 1B (PTP1B), a drug target for diabetes and cancer that catalyzes the dephosphorylation of numerous substrates in essential signaling pathways. By combining new experimental and computational data on WT-PTP1B and ≥10 PTP1B variants in multiple states, we discovered a fundamental and evolutionarily conserved CH/π switch that is critical for positioning the catalytically important WPD loop...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212749/comparative-analysis-of-single-cell-rna-sequencing-methods
#14
Christoph Ziegenhain, Beate Vieth, Swati Parekh, Björn Reinius, Amy Guillaumet-Adkins, Martha Smets, Heinrich Leonhardt, Holger Heyn, Ines Hellmann, Wolfgang Enard
Single-cell RNA sequencing (scRNA-seq) offers new possibilities to address biological and medical questions. However, systematic comparisons of the performance of diverse scRNA-seq protocols are lacking. We generated data from 583 mouse embryonic stem cells to evaluate six prominent scRNA-seq methods: CEL-seq2, Drop-seq, MARS-seq, SCRB-seq, Smart-seq, and Smart-seq2. While Smart-seq2 detected the most genes per cell and across cells, CEL-seq2, Drop-seq, MARS-seq, and SCRB-seq quantified mRNA levels with less amplification noise due to the use of unique molecular identifiers (UMIs)...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212748/systematic-investigation-of-transcription-factor-activity-in-the-context-of-chromatin-using-massively-parallel-binding-and-expression-assays
#15
Michal Levo, Tali Avnit-Sagi, Maya Lotan-Pompan, Yael Kalma, Adina Weinberger, Zohar Yakhini, Eran Segal
Precise gene expression patterns are established by transcription factor (TFs) binding to regulatory sequences. While these events occur in the context of chromatin, our understanding of how TF-nucleosome interplay affects gene expression is highly limited. Here, we present an assay for high-resolution measurements of both DNA occupancy and gene expression on large-scale libraries of systematically designed regulatory sequences. Our assay reveals occupancy patterns at the single-cell level. It provides an accurate quantification of the fraction of the population bound by a nucleosome and captures distinct, even adjacent, TF binding events...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212747/catalytic-independent-functions-of-parp-1-determine-sox2-pioneer-activity-at-intractable-genomic-loci
#16
Ziying Liu, W Lee Kraus
Pioneer transcription factors (TFs) function as genomic first responders, binding to inaccessible regions of chromatin to promote enhancer formation. The mechanism by which pioneer TFs gain access to chromatin remains an important unanswered question. Here we show that PARP-1, a nucleosome-binding protein, cooperates with intrinsic properties of the pioneer TF Sox2 to facilitate its binding to intractable genomic loci in embryonic stem cells. These actions of PARP-1 occur independently of its poly(ADP-ribosyl) transferase activity...
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212746/jekyll-hyde-the-other-life-of-the-death-ligand-trail
#17
Najoua Lalaoui, John Silke
Henry and Martin (2017) and Hartwig et al. (2017) provide more insights into the non-apoptotic function of the FADD/caspase-8 duo in TRAIL signaling.
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212745/expanding-the-crispr-toolbox-targeting-rna-with-cas13b
#18
Rodolphe Barrangou, Charles A Gersbach
In this issue of Molecular Cell, Smargon et al. (2017) unearth Cas13b from type VI-B CRISPR-Cas immune systems and characterize its RNA-guided, RNA-targeting activity, including regulation by the novel co-factors Csx27 and Csx28, as well as non-specific collateral RNA damage.
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28212744/parp1-and-sox2-an-unlikely-team-of-pioneers-to-conquer-the-nucleosome
#19
Guillaume Gaullier, Karolin Luger
In this issue of Molecular Cell, Liu and Kraus (2017) demonstrate that the pioneer transcription factor Sox2 requires PARP1 to bind to a subset of its recognition motifs, which are located within nucleosomes across the genome.
February 16, 2017: Molecular Cell
https://www.readbyqxmd.com/read/28190769/paf1-has-distinct-roles-in-transcription-elongation-and-differential-transcript-fate
#20
Harry Fischl, Françoise S Howe, Andre Furger, Jane Mellor
RNA polymerase II (Pol2) movement through chromatin and the co-transcriptional processing and fate of nascent transcripts is coordinated by transcription elongation factors (TEFs) such as polymerase-associated factor 1 (Paf1), but it is not known whether TEFs have gene-specific functions. Using strand-specific nucleotide resolution techniques, we show that levels of Paf1 on Pol2 vary between genes, are controlled dynamically by environmental factors via promoters, and reflect levels of processing and export factors on the encoded transcript...
February 16, 2017: Molecular Cell
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