Project description:Bottom-up proteomics database search algorithms used for peptide identification cannot comprehensively identify posttranslational modifications (PTMs) in a single-pass because of high false discovery rates (FDRs). A new approach to database searching enables Global PTM (G-PTM) identification by exclusively looking for curated PTMs, thereby avoiding the FDR penalty experienced during conventional variable modification searches. We identified nearly 2500 unique, high-confidence modified peptides comprising 31 different PTM types in single-pass database searches.
Project description:Bottom-up proteomics database search algorithms used for peptide identification cannot comprehensively identify posttranslational modifications (PTMs) in a single-pass because of high false discovery rates (FDRs). A new approach to database searching enables Global PTM (G-PTM) identification by exclusively looking for curated PTMs, thereby avoiding the FDR penalty experienced during conventional variable modification searches. We identified nearly 2500 unique, high-confidence modified peptides comprising 31 different PTM types in single-pass database searches. Male C57BL/6J (B6) and CAST/EiJ (CAST) mice were purchased from The Jackson Laboratories (Bar Harbor, Maine) and housed in an environmentally controlled vivarium at the University of Wisconsin Biochemistry Department. Mice were provided standard rodent chow (Purina no. 5008) and water ad libitum, and maintained on a 12-hour light/dark cycle (6 AM – 6 PM). At 10 weeks of age, mice were sacrificed by CO2 asphyxiation. All animal procedures were preapproved by the University of Wisconsin Animal Care and Use Committee.
Project description:Background: Histone post-translational modifications (PTMs) constitute a branch of epigenetic mechanisms that can control the expression of eukaryotic genes in a heritable manner. Recent studies have identified several PTM-binding proteins containing diverse specialized domains whose recognition of specific PTM sites leads to gene activation or repression. Here, we present a high-throughput proteogenomic platform designed to characterize the nucleosomal make-up of chromatin enriched with a set of histone PTM-binding proteins known as histone PTM readers. We support our findings with gene expression data correlating to PTM distribution. Results: We isolated human mononucleosomes bound by the bromodomain-containing proteins Brd2, Brd3 and Brd4, and by the chromodomain-containing heterochromatin proteins HP1alpha and HP1beta. Histone PTMs were quantified by mass spectrometry (ChIP-qMS), and their associated DNAs were mapped using deep sequencing. Our results reveal that Brd- and HP1-bound nucleosomes are enriched in histone PTMs consistent with actively transcribed euchromatin and silent heterochromatin, respectively. Data collected using RNA-Seq (GSM301568) show that Brd-bound sites correlate with highly expressed genes. In particular, Brd3 and Brd4 are most enriched on nucleosomes located within HOX gene clusters, whose expression is reduced upon Brd4 depletion by shRNA. Conclusions: Proteogenomic mapping of histone PTM readers, alongside the characterization of their local chromatin environments and transcriptional information, should prove useful for determining how histone PTMs are bound by these readers and how they contribute to distinct transcriptional states. Examination of Brd and HP1 proteins-binding sites in HEK293 cells.
Project description:Background: Histone post-translational modifications (PTMs) constitute a branch of epigenetic mechanisms that can control the expression of eukaryotic genes in a heritable manner. Recent studies have identified several PTM-binding proteins containing diverse specialized domains whose recognition of specific PTM sites leads to gene activation or repression. Here, we present a high-throughput proteogenomic platform designed to characterize the nucleosomal make-up of chromatin enriched with a set of histone PTM-binding proteins known as histone PTM readers. We support our findings with gene expression data correlating to PTM distribution. Results: We isolated human mononucleosomes bound by the bromodomain-containing proteins Brd2, Brd3 and Brd4, and by the chromodomain-containing heterochromatin proteins HP1alpha and HP1beta. Histone PTMs were quantified by mass spectrometry (ChIP-qMS), and their associated DNAs were mapped using deep sequencing. Our results reveal that Brd- and HP1-bound nucleosomes are enriched in histone PTMs consistent with actively transcribed euchromatin and silent heterochromatin, respectively. Data collected using RNA-Seq (GSM301568) show that Brd-bound sites correlate with highly expressed genes. In particular, Brd3 and Brd4 are most enriched on nucleosomes located within HOX gene clusters, whose expression is reduced upon Brd4 depletion by shRNA. Conclusions: Proteogenomic mapping of histone PTM readers, alongside the characterization of their local chromatin environments and transcriptional information, should prove useful for determining how histone PTMs are bound by these readers and how they contribute to distinct transcriptional states. Comparison of Brd2 and HP1b shRNA knockdown HEK293 cells to control knockdown HEK293 cells.
Project description:We profiled the enrichment of active (H3K4me1, H3K4me3, H3K27ac) and inactive (H3K9me3, H3K27me3) histone PTMs in cells that are wild-type (WT) or knock-out (KO) for the H3.3-specific chaperone HIRA. We performed native ChIP-seq following MNase digestion to isolate nucleosomes in H3.1-SNAP and H3.3-SNAP-bearing HeLa cells. We had previously assayed the distribution of the H3.1 and H3.3 histone variants (Gatto et al., 2022) in the same cell lines, so we generated this PTM ChIP-seq data to compare the behaviour of the variants with that of H3 modifications.
Project description:Protein post-translational modification (PTMs) enable cells to rapidly change in response to biological stimuli. With over 400 PTMs, understanding these control mechanisms is complex. To date, efforts have focused on investigating the effect of single PTMs on protein function. Yet, many proteins contain multiple PTMs. Moreover, one PTM can alter the prevalence of another; a phenomenon termed PTM crosstalk. Understanding PTM crosstalk is critical; however, its detection is challenging since PTMs occur sub-stoichiometrically. In this work, we developed an enrichment-free, label-free proteomics method that utilized high field asymmetric ion mobility spectrometry (FAIMS) to enhance the detection of PTM crosstalk. We showed that by searching for multiple combinations of dynamic PTMs on peptide sequences, a large increase in identifications of candidate PTM crosstalk sites was observed compared with standard LC-MS/MS. Additionally, by cycling through FAIMS compensation voltages within a single LC-FAIMS-MS/MS run, we showed that our LC-FAIMS-MS/MS workflow could increase multi-PTM containing peptide identifications without additional increases in run times. With more novel candidate crosstalk sites identified, we envisage LC-FAIMS-MS/MS to play an important role in expanding the repertoire of multi-PTM identifications. Moreover, it is only by detecting PTM crosstalk, that we can ‘see’ the full picture of how proteins are regulated.
Project description:Chromatin structure and function is maintained by dynamic protein-protein and protein-nucleic acid interactions. Histones are a family of proteins that are abundant chromatin constituents and that carry numerous post-translational modifications (PTMs). Histone PTMs mediate a variety of biological activities, including recruitment of enzymatic readers, writers and erasers that modulate protein activities, DNA replication, transcription and repair. Individual histone molecules contain multiple co-existing PTMs some of which exhibit crosstalk, i.e. coordinated or mutually exclusive activities. We here present an integrated experimental and computational approach for systems level molecular characterization of PTMs and PTM crosstalk. Using wildtype and engineered mouse embryonic stem cells with perturbations in the Polycomb Repressive Complex 1 (PRC1, suz12-/-), PRC2 (Ring1A/b-/-) and DNA methyltransferases (Dnmt1/3a/3b-/-) we performed comprehensive PTM analysis of histone H3 tails. We identified unique histone H3 PTM features of each of the four cell lines and we detected common combinatorial PTM features across cell lines. Using quantitative middle-down proteomics combined with probabilistic and statistical data analysis we extracted histone H3 PTM profiles for all four mESC systems. PTM crosstalk emerged as mutually exclusive histone PTMs or coordinately regulated PTMs independent of histone peptide abundance in the four model systems. We detected positive crosstalk between adjacent mono-methylated marks but strong negative crosstalk among most of the seven characterized di- and tri-methylations on lysines. We report novel features of PTM interplay involving hitherto poorly characterized arginine methylation and lysine methylation sites in histone H3, including H3R2me, H3R8me and H3K37me, which exhibited specific PTM codes suggesting a particular role in chromatin. All histone H3 PTM data is available in our publicly available CrossTalkDB repository at http://crosstalkdb.bmb.sdu.dk
Project description:Background: Histone post-translational modifications (PTMs) constitute a branch of epigenetic mechanisms that can control the expression of eukaryotic genes in a heritable manner. Recent studies have identified several PTM-binding proteins containing diverse specialized domains whose recognition of specific PTM sites leads to gene activation or repression. Here, we present a high-throughput proteogenomic platform designed to characterize the nucleosomal make-up of chromatin enriched with a set of histone PTM-binding proteins known as histone PTM readers. We support our findings with gene expression data correlating to PTM distribution. Results: We isolated human mononucleosomes bound by the bromodomain-containing proteins Brd2, Brd3 and Brd4, and by the chromodomain-containing heterochromatin proteins HP1alpha and HP1beta. Histone PTMs were quantified by mass spectrometry (ChIP-qMS), and their associated DNAs were mapped using deep sequencing. Our results reveal that Brd- and HP1-bound nucleosomes are enriched in histone PTMs consistent with actively transcribed euchromatin and silent heterochromatin, respectively. Data collected using RNA-Seq (GSM301568) show that Brd-bound sites correlate with highly expressed genes. In particular, Brd3 and Brd4 are most enriched on nucleosomes located within HOX gene clusters, whose expression is reduced upon Brd4 depletion by shRNA. Conclusions: Proteogenomic mapping of histone PTM readers, alongside the characterization of their local chromatin environments and transcriptional information, should prove useful for determining how histone PTMs are bound by these readers and how they contribute to distinct transcriptional states.
Project description:Background: Histone post-translational modifications (PTMs) constitute a branch of epigenetic mechanisms that can control the expression of eukaryotic genes in a heritable manner. Recent studies have identified several PTM-binding proteins containing diverse specialized domains whose recognition of specific PTM sites leads to gene activation or repression. Here, we present a high-throughput proteogenomic platform designed to characterize the nucleosomal make-up of chromatin enriched with a set of histone PTM-binding proteins known as histone PTM readers. We support our findings with gene expression data correlating to PTM distribution. Results: We isolated human mononucleosomes bound by the bromodomain-containing proteins Brd2, Brd3 and Brd4, and by the chromodomain-containing heterochromatin proteins HP1alpha and HP1beta. Histone PTMs were quantified by mass spectrometry (ChIP-qMS), and their associated DNAs were mapped using deep sequencing. Our results reveal that Brd- and HP1-bound nucleosomes are enriched in histone PTMs consistent with actively transcribed euchromatin and silent heterochromatin, respectively. Data collected using RNA-Seq (GSM301568) show that Brd-bound sites correlate with highly expressed genes. In particular, Brd3 and Brd4 are most enriched on nucleosomes located within HOX gene clusters, whose expression is reduced upon Brd4 depletion by shRNA. Conclusions: Proteogenomic mapping of histone PTM readers, alongside the characterization of their local chromatin environments and transcriptional information, should prove useful for determining how histone PTMs are bound by these readers and how they contribute to distinct transcriptional states.
Project description:Post-translational modifications (PTMs) are under significant focus in molecular biomedicine due to their importance in signal transduction in most cellular and organismal processes. Identification of PTMs, determination of PTM location sites, discrimination between functional and inert PTMs, and quantification of their occupancies are demanding tasks, especially in the light of PTM crosstalk in each biosystem. On top of that, the study of each PTM often necessitates a particular experimental design. Computational approaches can identify the relevant PTMs in a biosystem and help to design follow-up experiments involving specific PTM enrichment. Here, we present a PTM-centric proteome informatic pipeline for prediction of most probable and relevant PTMs in mass spectrometry-based proteomics data and refining raw data search parameters based on the acquired knowledge. Using expression profiling, we identified cellular proteins that are differentially regulated in response to multikinase inhibitors dasatinib and staurosporine at four different concentrations. Computational enrichment analysis was employed to determine the potential PTMs of protein targets for both drugs. Finally, we conducted an additional round of database search with these predicted chemical modifications. Our pipeline helped analyze the enriched PTMs and even detected proteins that were not picked up in the initial search. Our findings support the idea of PTM-oriented searching of MS data in proteomics based on computational enrichment analysis.