The multiplexing capabilities of isobaric mass tag-based protein quantification, such as Tandem Mass Tags or Isobaric Tag for Relative and Absolute Quantitation have dramatically increased the scope of mass spectrometry-based proteomics studies. Not only does the technology allow for the simultaneous quantification of multiple samples in a single MS injection, but its seamless compatibility with extensive sample prefractionation methods allows for comprehensive studies of complex proteomes. However, reporter ion-based quantification has often been criticized for limited quantification accuracy due to interference from coeluting peptides and peptide fragments. In this study, we investigate the extent of this problem and propose an effective and easy-to-implement remedy that relies on spiking a 6-protein calibration mixture to the samples. We evaluated our ratio adjustment approach using two large scale TMT 10-plex data sets derived from a human cancer and noncancer cell line as well as E. coli cells grown at two different conditions. Furthermore, we analyzed a complex 2-proteome artificial sample mixture and investigated the precision of TMT and precursor ion intensity-based label free quantification. Studying the protein set identified by both methods, we found that differentially abundant proteins were assigned dramatically higher statistical significance when quantified using TMT. Data are available via ProteomeXchange with identifier PXD003346.

This study analyzes the proteomes and phospho-proteomes of isogenic DLD-1 cancer cells differing in karyotypes and chromosome stability. Chromosome doubling is shown to trigger more extensive changes in (phospho-)proteomes than chromosome instability, and activation of mitotic pathways may explain differential responses to mitotic inhibitors.

FilmArray Respiratory Panel (RP) (Idaho Technology, Inc., Salt Lake City, UT, USA) performance was retrospectively evaluated in respiratory samples collected from neonates in 2 reference neonatology units. Using the FilmArray RP assay, 121/152 (79.6%) samples were positive for at least 1 respiratory virus, while 31/152 (20.4%) were negative. FilmArray RP results were concordant in 68/72 (94.4%) respiratory samples tested with laboratory-developed real-time PCR assays, while in 4/72 (5.6%) samples, the FilmArray RP assay detected an additional virus (2 human rhinovirus/enterovirus and 2 bocavirus). In addition, FilmArray RP results for 70 of 80 (87.5%) respiratory samples tested were concordant with the Seegene Seeplex RV15® detection assay (Seegene, Inc., Seoul, South Korea), while 10/80 (12.5%) were discordant. The advantages of the FilmArray RP are the rapid detection of respiratory viruses (1 hour), the wide number of pathogens detectable in a single assay, and the reduced hands-on time.

Aneuploidy is a hallmark of most human tumors, but the molecular physiology of aneuploid cells is not well characterized. In this study, we screened cell surface biomarkers of approximately 300 proteins by multiparameter flow cytometry using multiple aneuploid model systems such as cell lines, patient samples, and mouse models. Several new biomarkers were identified with altered expression in aneuploid cells, including overexpression of the cellular prion protein CD230/PrP and the immunosuppressive cell surface enzyme ecto-5'-nucleotidase CD73. Functional analyses associated these alterations with increased cellular stress. An increased number of CD73 cells was observed in confluent cultures in aneuploid cells relative to their diploid counterparts. An elevated expression in CD230/PrP was observed in serum-deprived cells in association with increased generation of reactive oxygen species. Overall, our work identified biomarkers of aneuploid karyotypes, which suggest insights into the underlying molecular physiology of aneuploid cells. .

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PA28γ (also known as PSME3), a nuclear activator of the 20S proteasome, is involved in the degradation of several proteins regulating cell growth and proliferation and in the dynamics of various nuclear bodies, but its precise cellular functions remain unclear. Here, using a quantitative FLIM-FRET based microscopy assay monitoring close proximity between nucleosomes in living human cells, we show that PA28γ controls chromatin compaction. We find that its depletion induces a decompaction of pericentromeric heterochromatin, which is similar to what is observed upon the knockdown of HP1β (also known as CBX1), a key factor of the heterochromatin structure. We show that PA28γ is present at HP1β-containing repetitive DNA sequences abundant in heterochromatin and, importantly, that HP1β on its own is unable to drive chromatin compaction without the presence of PA28γ. At the molecular level, we show that this novel function of PA28γ is independent of its stable interaction with the 20S proteasome, and most likely depends on its ability to maintain appropriate levels of H3K9me3 and H4K20me3, histone modifications that are involved in heterochromatin formation. Overall, our results implicate PA28γ as a key factor involved in the regulation of the higher order structure of chromatin.

<p>Description of the Supplementary Files</p>

No abstract