Structural study of human MRE11-RAD50-NBS1 (MRN) complex by crosslinking mass spectrometry
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ABSTRACT: A chemical crosslinking-mass spectrometry (CX-MS) experiment was performed to study the structure of the human MRN complex in the presence of ATM and DNA.
Project description:The mass spectrometry data of a previous publication (Chen et.al. 2009 doi:10.1038/emboj.2009.401) were reprocesed and is used for method developing, teaching and training purpose.
Project description:Structural maintenance of chromosomes (SMC)-kleisin complexes organize chromosomal DNAs in all domains of life, where they have key roles in chromosome segregation, DNA repair and regulation of gene expression. They function through topological entrapment and active translocation of DNA, but the underlying conformational changes are largely unclear. Using structural biology, mass spectrometry and cross-linking, we investigated the architecture of two evolutionarily distant SMC-kleisin complexes: proteobacterial MukBEF and eukaryotic cohesin. We show that both contain a dynamic coiled-coil discontinuity, the elbow, near the middle of their arms that permits a folded conformation. Bending at the elbow brings into proximity the hinge dimerization domain and the head/kleisin module, situated at opposite ends of the arms. Our findings favor SMC activity models that include a large conformational change in the arms, such as a relative movement between DNA binding sites during DNA loading and translocation
Project description:PleasStructural maintenance of chromosomes (SMC)-kleisin complexes organize chromosomal DNAs in all domains of life, where they have key roles in chromosome segregation, DNA repair and regulation of gene expression. They function through topological entrapment and active translocation of DNA, but the underlying conformational changes are largely unclear. Using structural biology, mass spectrometry and cross-linking, we investigated the architecture of two evolutionarily distant SMC-kleisin complexes: proteobacterial MukBEF and eukaryotic cohesin. We show that both contain a dynamic coiled-coil discontinuity, the elbow, near the middle of their arms that permits a folded conformation. Bending at the elbow brings into proximity the hinge dimerization domain and the head/kleisin module, situated at opposite ends of the arms. Our findings favor SMC activity models that include a large conformational change in the arms, such as a relative movement between DNA binding sites during DNA loading and translocatione provide an overall description of your study, think something similar in scope to the manuscript abstract
Project description:The Fanconi Anemia (FA) pathway repairs DNA damage caused by endogenous and chemotherapy-induced DNA crosslinks. Genetic inactivation of this pathway impairs development, prevents blood production and promotes cancer. The key molecular step in the FA pathway is the monoubiquitination of a heterodimer of FANCI-FANCD2 by the FA core complex - a megadalton multiprotein E3 ubiquitin ligase. Monoubiquitinated FANCI-FANCD2 then activates a pathway to remove the DNA crosslink. Lack of molecular insight into the FA core complex limits a detailed explanation of how this vital DNA repair pathway functions. Here we reconstituted an active, recombinant FA core complex, and used electron cryo-microscopy (cryo-EM) and mass spectrometry to determine its overall structure. The FA core complex is comprised of a central symmetric dimer of the FANCB and FAAP100 subunits, flanked by two copies of the RING finger protein, FANCL. This acts as a scaffold to assemble the remaining five subunits, resulting in an extended asymmetric structure. The two FANCL subunits are positioned at opposite ends of the complex in an unusual asymmetric arrangement, distinct from other E3 ligases. We propose that each of the two FANCL subunits play unique roles within the complex – one is a structural component while the other monoubiquitinates FANCD2. The cryo-EM structure of the FA core complex, supported by crosslinking mass spectrometry and native mass spectrometry, therefore provides a foundation for a detailed understanding of this fundamental DNA repair pathway.
Project description:To better understand human ATP13A2-mediated polyamine transport, we used single-particle cryo-electron microscopy to solve high-resolution structures of human ATP13A2. Interestingly, we found polyamine binding at multiple sites distributed along the transmembrane regions in ATP13A2 protein, which has not been reported in previous studies. Therefore, we used cross-linking mass spectrometry (CX-MS) to confirm potential binding sites.
Project description:Proteome-wide crosslinking mass spectrometry studies have coincided with the advent of MS-cleavable crosslinkers that can reveal the individual masses of the two crosslinked peptides. However, recently such studies have also been published with non-cleavable crosslinkers suggesting that MS-cleavability is not essential. We therefore examined in detail the advantages and disadvantages of using the commonly used MS-cleavable crosslinker, DSSO. Indeed, DSSO gave rise to signature peptide fragments with a distinct mass difference (doublet) for nearly all identified crosslinked peptides. Surprisingly, we could show that it was not these peptide masses that proved the main advantage of MS-cleavability of the crosslinker, but improved peptide backbone fragmentation which reduces ambiguity of peptide identifications. This also holds true for another commonly used MS-cleavable crosslinker, DSBU. We show, furthermore, that the more intricate MS3-based data acquisition approaches lack sensitivity and specificity, causing them to be outperformed by the simpler and faster stepped HCD method. This understanding will guide future developments and applications of proteome-wide crosslinking mass spectrometry.
Project description:Quantitative cross-linking/mass spectrometry (QCLMS) provides increasing structural detail on altered protein states in solution. Accurate quantitation is a value in itself but may also be central to elucidating small differences between protein states. Hence, QCLMS could benefit from data independent acquisition (DIA) which generally provides higher reproducibility than data dependent acquisition (DDA) and higher throughput than targeted methods. Therefore we here open DIA to QCLMS by extending a widely used DIA software, Spectronaut to now also accommodate cross-link data. A mixture of seven proteins cross-linked with bis[sulfosuccinimidyl] suberate (BS3) was used to evaluate this workflow. Out of the 414 identified unique residue pairs, 292 (70%) were quantifiable across triplicates with a coefficient of variation (CV) of 9.8%, with manual correction of peak selection and boundaries for PSMs in the lower quartile of individual CV values. This compares favourably to DDA where we previously quantified only 63% of the identified cross-links across triplicates with a CV of 14%, for a single protein and complete manual data curation. DIA QCLMS is promising to detect differential abundance of cross-linked peptides in complex mixtures despite the encountered ratio compression when increasing sample complexity through the addition of E. coli cell lysate as matrix. In conclusion, DIA software Spectronaut can now be used in cross-linking and DIA is indeed able to improve QCLMS.
Project description:Reanalysis of a cross-linked ribosomal cellular fraction dataset, that is a subset of a fragmentation parameters optimization dataset (PRIDE project PXD006131). The HCD fragmented part of the dataset was searched with the Cross-Linking MS identification tools OpenPepXL, pLink2, Kojak and XiSearch.
Project description:Vertebrate DNA crosslink repair excises toxic replication-blocking DNA crosslinks. Numerous factors involved in crosslink repair have been identified, and mutations in their corresponding genes cause Fanconi anemia (FA). A key step in crosslink repair is monoubiquitination of the FANCD2-FANCI heterodimer, which then recruits nucleases to remove the DNA lesion. In this study, monoubiquitinated FANCD2-FANCI complex was characterized using crosslinking mass spectrometry in order to provide in sights into the 3D structure of the complex.
Project description:Myosin motors are critical for diverse motility functions ranging from cytokinesis and endocytosis to muscle contraction. The UNC-45 chaperone controls myosin function mediating the folding, assembly, and degradation of the muscle protein. Here, we analyze the molecular mechanism of UNC-45 as a hub in myosin quality control. We show that UNC-45 forms discrete complexes with folded and unfolded myosin, forwarding them to downstream chaperones and E3 ligases. Structural analysis of a minimal chaperone:substrate complex reveals that UNC-45 binds to a conserved FX3HY motif in the myosin motor domain. Disrupting the observed interface by mutagenesis prevents myosin maturation leading to protein aggregation in vivo. We also show that a mutation in the FX3HY motif linked to the Freeman Sheldon Syndrome impairs UNC-45 assisted folding, reducing the level of functional myosin. These findings demonstrate that a faulty myosin quality control is a critical yet unexplored cause of human myopathies.