Life Science Alliance最新文献

Eukaryotic gene expression is regulated at the transcriptional and post-transcriptional levels, with disruption of regulation contributing significantly to human diseases. The 5' m7G mRNA cap is a central node in post-transcriptional regulation, participating in both mRNA stabilization and translation efficiency. In mammals, DCP1a and DCP1b are paralogous cofactor proteins of the mRNA cap hydrolase DCP2. As lower eukaryotes have a single DCP1 cofactor, the functional advantages gained by this evolutionary divergence remain unclear. We report the first functional dissection of DCP1a and DCP1b, demonstrating that they are non-redundant cofactors of DCP2 with unique roles in decapping complex integrity and specificity. DCP1a is essential for decapping complex assembly and interactions between the decapping complex and mRNA cap-binding proteins. DCP1b is essential for decapping complex interactions with protein degradation and translational machinery. DCP1a and DCP1b impact the turnover of distinct mRNAs. The observation that different ontological groups of mRNA molecules are regulated by DCP1a and DCP1b, along with their non-redundant roles in decapping complex integrity, provides the first evidence that these paralogs have qualitatively distinct functions.

Sickle cell disease (SCD) is the most common inherited monogenetic disorder. Chronic and acute pain are hallmark features of SCD involving neural and vascular injury and inflammation. Mast cells reside in the vicinity of nerve fibers and vasculature, but how they influence these structures remains unknown. We therefore examined the mechanism of mast cell activation in a sickle microenvironment replete with cell-free heme and inflammation. Mast cells exposed to this environment showed an explosion of nuclear contents with the release of citrullinated histones, suggestive of mast cell extracellular trap (MCET) release. MCETs interacted directly with the vasculature and nerve fibers, a cause of vascular and neural injury in sickle cell mice. MCET formation was dependent upon peptidylarginine deiminase 4 (PAD4). Inhibition of PAD4 ameliorated vasoocclusion, chronic and acute hyperalgesia, and inflammation in sickle mice. PAD4 activation may also underlie neutrophil trap formation in SCD, thus providing a novel target to treat the sequelae of vascular and neural injury in SCD.

Sleep and circadian rhythm dysfunctions are common clinical features of Alzheimer's disease (AD). Increasing evidence suggests that in addition to being a symptom, sleep disturbances can also drive the progression of neurodegeneration. Protein aggregation is a pathological hallmark of AD; however, the molecular pathways behind how sleep affects protein homeostasis remain elusive. Here we demonstrate that sleep modulation influences proteostasis and the progression of neurodegeneration in Drosophila models of tauopathy. We show that sleep deprivation enhanced Tau aggregational toxicity resulting in exacerbated synaptic degeneration. In contrast, sleep induction using gaboxadol led to reduced toxic Tau accumulation in neurons as a result of modulated autophagic flux and enhanced clearance of ubiquitinated Tau, suggesting altered protein processing and clearance that resulted in improved synaptic integrity and function. These findings highlight the complex relationship between sleep and regulation of protein homeostasis and the neuroprotective potential of sleep-enhancing therapeutics to slow the progression or delay the onset of neurodegeneration.

Cockayne syndrome (CS) is a premature ageing condition characterized by microcephaly, growth failure, and neurodegeneration. It is caused by mutations in ERCC6 or ERCC8 encoding for Cockayne syndrome B (CSB) and A (CSA) proteins, respectively. CSA and CSB have well-characterized roles in transcription-coupled nucleotide excision repair, responsible for removing bulky DNA lesions, including those caused by UV irradiation. Here, we report that CSA dysfunction causes defects in the nuclear envelope (NE) integrity. NE dysfunction is characteristic of progeroid disorders caused by a mutation in NE proteins, such as Hutchinson-Gilford progeria syndrome. However, it has never been reported in Cockayne syndrome. We observed CSA dysfunction affected LEMD2 incorporation at the NE and increased actin stress fibers that contributed to enhanced mechanical stress to the NE. Altogether, these led to NE abnormalities associated with the activation of the cGAS/STING pathway. Targeting the linker of the nucleoskeleton and cytoskeleton complex was sufficient to rescue these phenotypes. This work reveals NE dysfunction in a progeroid syndrome caused by mutations in a DNA damage repair protein, reinforcing the connection between NE deregulation and ageing.

Mitochondrial gene expression is a compartmentalised process essential for metabolic function. The replication and transcription of mitochondrial DNA (mtDNA) take place at nucleoids, whereas the subsequent processing and maturation of mitochondrial RNA (mtRNA) and mitoribosome assembly are localised to mitochondrial RNA granules. The bidirectional transcription of circular mtDNA can lead to the hybridisation of polycistronic transcripts and the formation of immunogenic mitochondrial double-stranded RNA (mt-dsRNA). However, the mechanisms that regulate mt-dsRNA localisation and homeostasis are largely unknown. With super-resolution microscopy, we show that mt-dsRNA overlaps with the RNA core and associated proteins of mitochondrial RNA granules but not nucleoids. Mt-dsRNA foci accumulate upon the stimulation of cell proliferation and their abundance depends on mitochondrial ribonucleotide supply by the nucleoside diphosphate kinase, NME6. Consequently, mt-dsRNA foci are profuse in cultured cancer cells and malignant cells of human tumour biopsies. Our results establish a new link between cell proliferation and mitochondrial nucleic acid homeostasis.

Chromatin regulators alter the physical properties of chromatin to make it more or less permissive to transcription by modulating another protein's access to a specific DNA sequence through changes in nucleosome occupancy or histone modifications at a particular locus. Mammalian SWI/SNF complexes are a group of ATPase-dependent chromatin remodelers. In mouse embryonic stem cells, there are three primary forms of mSWI/SNF: canonical BAF (cBAF), polybromo-associated BAF (pBAF), and GLTSCR-associated BAF (gBAF). Nkx2-9 is bivalent, meaning nucleosomes at the locus have active and repressive modifications. In this study, we used unique BAF subunits to recruit each of the three complexes to Nkx2-9 using dCas9-mediated inducible recruitment (FIRE-Cas9). We show that recruitment of cBAF complexes leads to a significant loss of the polycomb repressive-2 H3K27me3 histone mark and polycomb repressive-1 and repressive-2 complex proteins, whereas gBAF and pBAF do not. Moreover, nucleosome occupancy alone cannot explain the loss of these marks. Our results demonstrate that cBAF has a unique role in the direct opposition of polycomb-associated histone modifications that gBAF and pBAF do not share.

Many ATP-binding cassette transporters are regulated by phosphorylation on long and disordered loops which presents a challenge to visualize with structural methods. We have trapped an activated state of the regulatory domain (R-domain) of yeast cadmium factor 1 (Ycf1) by enzymatically enriching the phosphorylated state. A 3.23 Å cryo-EM structure reveals an R-domain structure with four phosphorylated residues and the position for the entire R-domain. The structure reveals key R-domain interactions including a bridging interaction between NBD1 and NBD2 and an interaction with the R-insertion, another regulatory region. We scanned these interactions by systematically replacing segments along the entire R-domain with scrambled combinations of alanine, glycine, and glutamine and probing function under cellular conditions that require the Ycf1 function. We find a close match with these interactions and interacting regions on our R-domain structure that points to the importance of most well-structured segments for function. We propose a model where the R-domain stabilizes a transport-competent state upon phosphorylation by enveloping NBD1 entirely.

Helicobacter pylori infection predisposes carriers to a high risk of developing gastric cancer. The cell-of-origin of antral gastric cancer is the Lgr5⁺ stem cell. Here, we show that infection of antrum-derived gastric organoid cells with H. pylori increases the expression of the stem cell marker Lgr5 as determined by immunofluorescence microscopy, qRT-PCR, and Western blotting, both when cells are grown and infected as monolayers and when cells are exposed to H. pylori in 3D structures. H. pylori exposure increases stemness properties as determined by spheroid formation assay. Lgr5 expression and the acquisition of stemness depend on a functional type IV secretion system (T4SS) and at least partly on the T4SS effector CagA. The pharmacological inhibition or genetic ablation of NF-κB reverses the increase in Lgr5 and spheroid formation. Constitutively active Wnt/β-catenin signaling because of Apc inactivation exacerbates H. pylori-induced Lgr5 expression and stemness, both of which persist even after eradication of the infection. The combined data indicate that H. pylori has stemness-inducing properties that depend on its ability to activate NF-κB signaling.