Substrate relay in an Hsp70-cochaperone cascade safeguards tail-anchored membrane protein targeting
Membrane proteins are aggregation-prone in aqueous environments, and their biogenesis poses acute challenges to cellular protein homeostasis. How the chaperone network effectively protects integral membrane proteins during their post-translational targeting is not well understood. Here, biochemical reconstitutions showed that the yeast cytosolic Hsp70 is responsible for capturing newly synthesized tail-anchored membrane proteins (TAs) in the soluble form. Moreover, direct interaction of Hsp70 with the cochaperone Sgt2 initiates a sequential series of TA relays to the dedicated TA targeting factor Get3. In contrast to direc...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Cho, H., Shan, S.-o. Tags: Membrane & Intracellular Transport, Protein Biosynthesis & Quality Control Articles Source Type: research
Acidic cell elongation drives cell differentiation in the Arabidopsis root
In multicellular systems, the control of cell size is fundamental in regulating the development and growth of the different organs and of the whole organism. In most systems, major changes in cell size can be observed during differentiation processes where cells change their volume to adapt their shape to their final function. How relevant changes in cell volume are in driving the differentiation program is a long-standing fundamental question in developmental biology. In the Arabidopsis root meristem, characteristic changes in the size of the distal meristematic cells identify cells that initiated the differentiation prog...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Pacifici, E., Di Mambro, R., Dello Ioio, R., Costantino, P., Sabatini, S. Tags: Development & Differentiation, Plant Biology, Signal Transduction Articles Source Type: research
A temporally dynamic Foxp3 autoregulatory transcriptional circuit controls the effector Treg programme
Regulatory T cells (Treg) are negative regulators of the immune response; however, it is poorly understood whether and how Foxp3 transcription is induced and regulated in the periphery during T-cell responses. Using Foxp3-Timer of cell kinetics and activity (Tocky) mice, which report real-time Foxp3 expression, we show that the flux of new Foxp3 expressors and the rate of Foxp3 transcription are increased during inflammation. These persistent dynamics of Foxp3 transcription determine the effector Treg programme and are dependent on a Foxp3 autoregulatory transcriptional circuit. Persistent Foxp3 transcriptional activity co...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Bending, D., Paduraru, A., Ducker, C. B., Prieto Martin, P., Crompton, T., Ono, M. Tags: Immunology, Transcription Articles Source Type: research
A high-throughput method to identify trans-activation domains within transcription factor sequences
Even though transcription factors (TFs) are central players of gene regulation and have been extensively studied, their regulatory trans-activation domains (tADs) often remain unknown and a systematic functional characterization of tADs is lacking. Here, we present a novel high-throughput approach tAD-seq to functionally test thousands of candidate tADs from different TFs in parallel. The tADs we identify by pooled screening validate in individual luciferase assays, whereas neutral regions do not. Interestingly, the tADs are found at arbitrary positions within the TF sequences and can contain amino acid (e.g., glutamine) r...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Arnold, C. D., Nemcko, F., Woodfin, A. R., Wienerroither, S., Vlasova, A., Schleiffer, A., Pagani, M., Rath, M., Stark, A. Tags: Methods & Resources, Systems & Computational Biology, Transcription Source Type: research
Cdc48/p97 segregase is modulated by cyclin-dependent kinase to determine cyclin fate during G1 progression
Cells sense myriad signals during G1, and a rapid response to prevent cell cycle entry is of crucial importance for proper development and adaptation. Cln3, the most upstream G1 cyclin in budding yeast, is an extremely short-lived protein subject to ubiquitination and proteasomal degradation. On the other hand, nuclear accumulation of Cln3 depends on chaperones that are also important for its degradation. However, how these processes are intertwined to control G1-cyclin fate is not well understood. Here, we show that Cln3 undergoes a challenging ubiquitination step required for both degradation and full activation. Segrega...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Parisi, E., Yahya, G., Flores, A., Aldea, M. Tags: Cell Cycle, Post-translational Modifications, Proteolysis & Proteomics Articles Source Type: research
Cezanne/OTUD7B is a cell cycle-regulated deubiquitinase that antagonizes the degradation of APC/C substrates
The anaphase-promoting complex/cyclosome (APC/C) is an E3 ubiquitin ligase and key regulator of cell cycle progression. Since APC/C promotes the degradation of mitotic cyclins, it controls cell cycle-dependent oscillations in cyclin-dependent kinase (CDK) activity. Both CDKs and APC/C control a large number of substrates and are regulated by analogous mechanisms, including cofactor-dependent activation. However, whereas substrate dephosphorylation is known to counteract CDK, it remains largely unknown whether deubiquitinating enzymes (DUBs) antagonize APC/C substrate ubiquitination during mitosis. Here, we demonstrate that...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Bonacci, T., Suzuki, A., Grant, G. D., Stanley, N., Cook, J. G., Brown, N. G., Emanuele, M. J. Tags: Cell Cycle, Post-translational Modifications, Proteolysis & Proteomics Articles Source Type: research
NF-{kappa}B activation in astrocytes drives a stage-specific beneficial neuroimmunological response in ALS
Astrocytes are involved in non-cell-autonomous pathogenic cascades in amyotrophic lateral sclerosis (ALS); however, their role is still debated. We show that astrocytic NF-B activation drives microglial proliferation and leukocyte infiltration in the SOD1 (G93A) ALS model. This response prolongs the presymptomatic phase, delaying muscle denervation and decreasing disease burden, but turns detrimental in the symptomatic phase, accelerating disease progression. The transition corresponds to a shift in the microglial phenotype showing two effects that can be dissociated by temporally controlling NF-B activation. While NF-B ac...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Ouali Alami, N., Schurr, C., Olde Heuvel, F., Tang, L., Li, Q., Tasdogan, A., Kimbara, A., Nettekoven, M., Ottaviani, G., Raposo, C., Röver, S., Rogers-Evans, M., Rothenhäusler, B., Ullmer, C., Fingerle, J., Grether, U., Knuesel, I., Boeck Tags: Molecular Biology of Disease, Neuroscience Articles Source Type: research
Myc and the Tip60 chromatin remodeling complex control neuroblast maintenance and polarity in Drosophila
Stem cells establish cortical polarity and divide asymmetrically to simultaneously maintain themselves and generate differentiating offspring cells. Several chromatin modifiers have been identified as stemness factors in mammalian pluripotent stem cells, but whether these factors control stem cell polarity and asymmetric division has not been investigated so far. We addressed this question in Drosophila neural stem cells called neuroblasts. We identified the Tip60 chromatin remodeling complex and its interaction partner Myc as regulators of genes required for neuroblast maintenance. Knockdown of Tip60 complex members resul...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Rust, K., Tiwari, M. D., Mishra, V. K., Grawe, F., Wodarz, A. Tags: Cell Adhesion, Polarity & Cytoskeleton, Chromatin, Epigenetics, Genomics & Functional Genomics, Stem Cells Articles Source Type: research
RIM-binding proteins recruit BK-channels to presynaptic release sites adjacent to voltage-gated Ca2+-channels
The active zone of presynaptic nerve terminals organizes the neurotransmitter release machinery, thereby enabling fast Ca2+-triggered synaptic vesicle exocytosis. BK-channels are Ca2+-activated large-conductance K+-channels that require close proximity to Ca2+-channels for activation and control Ca2+-triggered neurotransmitter release by accelerating membrane repolarization during action potential firing. How BK-channels are recruited to presynaptic Ca2+-channels, however, is unknown. Here, we show that RBPs (for RIM-binding proteins), which are evolutionarily conserved active zone proteins containing SH3- and FN3-domains,...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Sclip, A., Acuna, C., Luo, F., Südhof, T. C. Tags: Membrane & Intracellular Transport, Neuroscience, Physiology Articles Source Type: research
The MRX complex regulates Exo1 resection activity by altering DNA end structure
Homologous recombination is triggered by nucleolytic degradation (resection) of DNA double-strand breaks (DSBs). DSB resection requires the Mre11-Rad50-Xrs2 (MRX) complex, which promotes the activity of Exo1 nuclease through a poorly understood mechanism. Here, we describe the Mre11-R10T mutant variant that accelerates DSB resection compared to wild-type Mre11 by potentiating Exo1-mediated processing. This increased Exo1 resection activity leads to a decreased association of the Ku complex to DSBs and an enhanced DSB resection in G1, indicating that Exo1 has a direct function in preventing Ku association with DSBs. Molecul...
Source: EMBO Journal - August 15, 2018 Category: Molecular Biology Authors: Gobbini, E., Cassani, C., Vertemara, J., Wang, W., Mambretti, F., Casari, E., Sung, P., Tisi, R., Zampella, G., Longhese, M. P. Tags: DNA Replication, Repair & Recombination Articles Source Type: research
Growing a gasdermin pore in membranes of pyroptotic cells
Inflammasome-activated caspase-1, caspase-11, caspase-4, and caspase-5 cleave GSDMD to unleash its N-terminal gasdermin-N domain (GSDMDNterm) that perforates the plasma membrane to execute pyroptosis and stimulate inflammation. The mechanism underlying GSDMDNterm pore formation is unclear. Mulvihill et al use high-resolution atomic force microscopy (AFM) to analyze the dynamic pore formation process of GSDMDNterm. GSDMDNterm protomers are inserted into the lipid membrane to assemble arc- or slit-shaped oligomers that can incorporate additional protomers and grow into large and stable ring-shaped oligomers to form pore...
Source: EMBO Journal - August 1, 2018 Category: Molecular Biology Authors: Ding, J., Shao, F. Tags: Autophagy & Cell Death, Immunology News [amp ] Views Source Type: research
A wobbly road to drug resistance in melanoma: tRNA-modifying enzymes in translation reprogramming
Alterations in transcript-specific translation are emerging as a driver of cellular transformation and cancer etiology. A new study provides evidence for enhanced codon-dependent translation of hypoxia-inducible factor 1α in promoting glycolytic metabolism and drug resistance in melanoma cells. This specialized translation reprogramming relies, in part, on mTORC2-mediated phosphorylation of enzymes modifying the wobble position of the transfer RNA anticodon. (Source: EMBO Journal)
Source: EMBO Journal - August 1, 2018 Category: Molecular Biology Authors: McMahon, M., Ruggero, D. Tags: Cancer, Molecular Biology of Disease News [amp ] Views Source Type: research
Proteolytic ectodomain shedding of membrane proteins in mammals--hardware, concepts, and recent developments
Proteolytic removal of membrane protein ectodomains (ectodomain shedding) is a post-translational modification that controls levels and function of hundreds of membrane proteins. The contributing proteases, referred to as sheddases, act as important molecular switches in processes ranging from signaling to cell adhesion. When deregulated, ectodomain shedding is linked to pathologies such as inflammation and Alzheimer's disease. While proteases of the "a disintegrin and metalloprotease" (ADAM) and "beta-site APP cleaving enzyme" (BACE) families are widely considered as sheddases, in recent years a much broader range of prot...
Source: EMBO Journal - August 1, 2018 Category: Molecular Biology Authors: Lichtenthaler, S. F., Lemberg, M. K., Fluhrer, R. Tags: Membrane & Intracellular Transport, Post-translational Modifications, Proteolysis & Proteomics Review Source Type: research
Shelterin promotes tethering of late replication origins to telomeres for replication-timing control
DNA replication initiates at many discrete loci on eukaryotic chromosomes, and individual replication origins are regulated under a spatiotemporal program. However, the underlying mechanisms of this regulation remain largely unknown. In the fission yeast Schizosaccharomyces pombe, the telomere-binding protein Taz1, ortholog of human TRF1/TRF2, regulates a subset of late replication origins by binding to the telomere-like sequence near the origins. Here, we showed using a lacO/LacI-GFP system that Taz1-dependent late origins were predominantly localized at the nuclear periphery throughout interphase, and were localized adja...
Source: EMBO Journal - August 1, 2018 Category: Molecular Biology Authors: Ogawa, S., Kido, S., Handa, T., Ogawa, H., Asakawa, H., Takahashi, T. S., Nakagawa, T., Hiraoka, Y., Masukata, H. Tags: Chromatin, Epigenetics, Genomics & Functional Genomics, DNA Replication, Repair & Recombination Articles Source Type: research
MST2 kinase suppresses rDNA transcription in response to DNA damage by phosphorylating nucleolar histone H2B
The heavily transcribed rDNA repeats that give rise to the ribosomal RNA are clustered in a unique chromatin structure, the nucleolus. Due to its highly repetitive nature and transcriptional activity, the nucleolus is considered a hotspot of genomic instability. Breaks in rDNA induce a transient transcriptional shut down to conserve energy and promote rDNA repair; however, how nucleolar chromatin is modified and impacts on rDNA repair is unknown. Here, we uncover that phosphorylation of serine 14 on histone H2B marks transcriptionally inactive nucleolar chromatin in response to DNA damage. We identified that the MST2 kinas...
Source: EMBO Journal - August 1, 2018 Category: Molecular Biology Authors: Pefani, D. E., Tognoli, M. L., Pirincci Ercan, D., Gorgoulis, V., O'Neill, E. Tags: Chromatin, Epigenetics, Genomics & Functional Genomics, DNA Replication, Repair & Recombination, Post-translational Modifications, Proteolysis & Proteomics Articles Source Type: research
