Nuclear pore complexes mediate subtelomeric gene silencing by regulating PCNA levels on chromatin.

The nuclear pore complex (NPC) physically interacts with chromatin and regulates gene expression. The Saccharomyces cerevisiae inner ring nucleoporin Nup170 has been implicated in chromatin organization and the maintenance of gene silencing in subtelomeric regions. To gain insight into how Nup170 regulates this process, we used protein-protein interactions, genetic interactions, and transcriptome correlation analyses to identify the Ctf18-RFC complex, an alternative proliferating cell nuclear antigen (PCNA) loader, as a facilitator of the gene regulatory functions of Nup170.

Viral protein engagement of GBF1 induces host cell vulnerability through synthetic lethality.

Viruses co-opt host proteins to carry out their lifecycle. Repurposed host proteins may thus become functionally compromised; a situation analogous to a loss-of-function mutation. We term such host proteins as viral-induced hypomorphs.

Viral protein engagement of GBF1 induces host cell vulnerability through synthetic lethality.

Unlabelled: Viruses co-opt host proteins to carry out their lifecycle. Repurposed host proteins may thus become functionally compromised; a situation analogous to a loss-of-function mutation. We term such host proteins viral-induced hypomorphs.

Crippling life support for SARS-CoV-2 and other viruses through synthetic lethality.

With the rapid global spread of SARS-CoV-2, we have become acutely aware of the inadequacies of our ability to respond to viral epidemics. Although disrupting the viral life cycle is critical for limiting viral spread and disease, it has proven challenging to develop targeted and selective therapeutics. Synthetic lethality offers a promising but largely unexploited strategy against infectious viral disease; as viruses infect cells, they abnormally alter the cell state, unwittingly exposing new vulnerabilities in the infected cell.

Large-Scale and Targeted Quantitative Cross-Linking MS Using Isotope-Labeled Protein Interaction Reporter (PIR) Cross-Linkers.

Quantitative measurement of chemically cross-linked proteins is crucial to reveal dynamic information about protein structures and protein-protein interactions and how these are differentially regulated during stress, aging, drug treatment, and most perturbations. Previously, we demonstrated how quantitative in vivo cross-linking (CL) with stable isotope labeling of amino acids in cell culture (SILAC) enables both heritable and dynamic changes in cells to be visualized. In this work, we demonstrate the technical feasibility of proteome-scale quantitative in vivo CL-MS using isotope-labeled protein interaction reporter (PIR) cross-linkers and E.

XLinkDB 2.0: integrated, large-scale structural analysis of protein crosslinking data.

Motivation: Large-scale chemical cross-linking with mass spectrometry (XL-MS) analyses are quickly becoming a powerful means for high-throughput determination of protein structural information and protein-protein interactions. Recent studies have garnered thousands of cross-linked interactions, yet the field lacks an effective tool to compile experimental data or access the network and structural knowledge for these large scale analyses. We present XLinkDB 2.

Spectral Library Searching To Identify Cross-Linked Peptides.

Methods harnessing protein cross-linking and mass spectrometry (XL-MS) offer high-throughput means to identify protein-protein interactions (PPIs) and structural interfaces of protein complexes. Yet, specialized data dependent methods and search algorithms are often required to confidently assign peptide identifications to spectra. To improve the efficiency of matching high confidence spectra, we developed a spectral library based approach to search cross-linked peptide data derived from Protein Interaction Reporter (PIR) methods using the spectral library search algorithm, SpectraST.

Parallel Spectral Acquisition with an Ion Cyclotron Resonance Cell Array.

Mass measurement accuracy is a critical analytical figure-of-merit in most areas of mass spectrometry application. However, the time required for acquisition of high-resolution, high mass accuracy data limits many applications and is an aspect under continual pressure for development. Current efforts target implementation of higher electrostatic and magnetic fields because ion oscillatory frequencies increase linearly with field strength.

Probing the protein interaction network of Pseudomonas aeruginosa cells by chemical cross-linking mass spectrometry.

In pathogenic Gram-negative bacteria, interactions among membrane proteins are key mediators of host cell attachment, invasion, pathogenesis, and antibiotic resistance. Membrane protein interactions are highly dependent upon local properties and environment, warranting direct measurements on native protein complex structures as they exist in cells. Here we apply in vivo chemical cross-linking mass spectrometry, to reveal the first large-scale protein interaction network in Pseudomonas aeruginosa, an opportunistic human pathogen, by covalently linking interacting protein partners, thereby fixing protein complexes in vivo.

H5N1 virus causes significant perturbations in host proteome very early in influenza virus-infected primary human monocyte-derived macrophages.

H5N1 influenza viruses, which cause disease in humans, have unusually high pathogenicity. The temporal response of primary human monocyte-derived macrophages infected with highly pathogenic H5N1 and seasonal H1N1 influenza viruses was evaluated using mass spectrometry-based quantitative proteomic profiling. This was done in order to demonstrate significant perturbation of the host proteome upon viral infection, as early as 1 hour after infection.

Quantitative proteomic analysis of HIV-1 infected CD4+ T cells reveals an early host response in important biological pathways: protein synthesis, cell proliferation, and T-cell activation.

Human immunodeficiency virus (HIV-1) depends upon host-encoded proteins to facilitate its replication while at the same time inhibiting critical components of innate and/or intrinsic immune response pathways. To characterize the host cell response on protein levels in CD4+ lymphoblastoid SUP-T1 cells after infection with HIV-1 strain LAI, we used mass spectrometry (MS)-based global quantitation with iTRAQ (isobaric tag for relative and absolute quantification). We found 266, 60 and 22 proteins differentially expressed (DE) (P-value ≤ 0.

Rapid direct analysis in real time (DART) mass spectrometric detection of juvenile hormone III and its terpene precursors.

Direct analysis in real time (DART) is a plasma-based ambient ionization technique that enables rapid ionization of small molecules with high sample throughput. In this work, DART was coupled to an orthogonal (oa) time-of-flight (TOF) mass spectrometer and the system was optimized for analyzing a vital hormonal regulator in insects, juvenile hormone (JH) III and its terpene precursors, namely, farnesol, farnesoic acid, and methyl farnesoate. Optimization experiments were planned using design of experiments (DOE) full factorial models to identify the most significant DART variables contributing to JH III analysis sensitivity by DART-TOF mass spectrometry (MS).

Inline pneumatically assisted atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry.

Atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) is known to suffer from poor ion transfer efficiencies as compared to conventional vacuum MALDI (vMALDI). To mitigate these issues, a new AP-MALDI ion source utilizing a coaxial gas flow was developed. Nitrogen, helium, and sulfur hexafluoride were tested for their abilities as ion carriers for a standard peptide and small drug molecules.