Biology subjects

Buch-Larsen, S. C.

Publications and source records attributed to Buch-Larsen, S. C..

6 recordsLinked to original sources

bioRxiv2026

An auto-generated ADP-ribosyl-cysteine degron drives DTX2-dependent turnover of PARP7

The mono-ADP-ribosyltransferase PARP7 exerts negative feedback on androgen receptor (AR) signaling by generating an ADP-ribosyl-cysteine degron on AR that marks it for degradation. Here we show that the protein half-life of PARP7 is set by cysteine auto-ADP-ribosylation, providing a mechanism for temporal control of its feedback on AR-dependent transcription in prostate cancer cells. ADP-ribosyl-cysteine in the PARP7 catalytic domain constitutes a degron read by the E3 ligase DTX2, driving PARP7 polyubiquitination and proteasomal degradation. Thus, the same E3 is used to degrade both PARP7 and its substrate AR. Using label-free mass spectrometry, we identify the AP-1 factor c-JUN as a PARP7 substrate and show that ADP-ribosylated c-JUN accumulates upon DTX2 depletion. ADP-ribosyl degron formation is dependent on NAD+ availability since depleting NAD+ pharmacologically or under hypoxia prevents degron formation and stabilizes PARP7 in a catalytically constrained state that compromises its feedback activity. Correlations between PARP7 expression and hypoxia signatures in prostate tumors, together with sensitivity to the PARP7-selective inhibitor RBN-2397 across cancer lines, nominate hypoxic, NAD+ depleted contexts as heightened vulnerability to PARP7-targeting agents. Marking transcription factors for degradation by covalent ADP-ribosylation is emerging as a distinct mode of transcriptional control.

biochemistry↗

bioRxiv2025

Deciphering cytokine-driven ADP-ribosylation signaling networks via Af1521-based mass spectrometry analysis of labile Glu/Asp-linkages

ADP-ribosylation (ADPr) is a regulatory post-translational modification targeting nine amino acid residues. Glutamate- and aspartate-linked ADPr (Glu/Asp-ADPr) is chemically unstable during sample preparation for conventional mass spectrometry (MS)-based proteomics workflows, limiting its detection. Here, we systematically assessed the stability of ADPr linkages using synthetic peptides and confirmed that ester-linked Glu/Asp-ADPr is lost under alkaline conditions, elevated temperatures, or through hydrolysis by wildtype Af1521. We established an acidic enrichment workflow encompassing an Af1521 mutant, robustly preserving Glu/Asp-ADPr enabling their site-specific and systems-wide MS analysis. Applying this strategy to cytokine-stimulated A549 and HeLa cells, we identified >600 Glu/Asp-ADPr and >200 Cys-ADPr sites. Our analysis uncovered that Glu/Asp-ADPr marks distinct cytoplasmic protein networks enriched in immune functions, contrasting with Ser-ADPr typically observed on nuclear and chromatin-associated proteins. Quantitative profiling revealed reproducible ADPr patterns specific to cell type and treatment. Notably, PARP10 promoted Glu/Asp modification of ubiquitin, highlighting crosstalk between ADPr and ubiquitin signaling. Across interferon treatments, we identified a conserved network of antiviral PARPs and associated cofactors extensively modified on Glu/Asp residues, emphasizing residue-specific ADPr as a regulator of innate immune signaling. Together, our work establishes an MS-based proteomics workflow for identification of Glu/Asp-ADPr, provides a resource of site-specific modification events, and reveals residue-specific ADPr dynamics in immune signaling.

cell biology↗

bioRxiv2023

A site-specific analysis of the ADP-Ribosylome unveils Homogeneous DNA Damage-Induced Serine ADP-Ribosylation across wild-type and BRCA-mutant Breast Cancer cell lines

ADP-ribosylation (ADPr) signaling plays a crucial role in the DNA damage response. Inhibitors against the main enzyme catalyzing ADPr after DNA damage - PARP1 - are used as targeted therapies against breast cancers with BRCA1/2 mutations. However, development of resistance to PARP inhibitors (PARPi) is a major obstacle in treating patients. To better understand the role of ADPr in PARPi sensitivity, we used Liquid Chromatography-Mass Spectrometry (LC-MS) for systems level analysis of the ADP-ribosylome in six breast cancer cell lines exhibiting different PARPi sensitivities. We identified 1,632 sites on 777 proteins across all cell lines, primarily on serine residues, with site-specific overlap of targeted residues across DNA damage-related proteins across all cell lines, demonstrating high conservation of serine ADPr signaling networks upon DNA damage. We furthermore observed site-specific differences in ADPr intensities in PARPi-sensitive BRCA mutants, and unique ADPr sites in PARPi-resistant BRCA mutant cells, which we notably show to have low PARG levels and longer ADPr chains on PARP1.

cell biology↗

bioRxiv2022

A quantitative and site-specific atlas of the in vivo citrullinome reveals widespread existence of citrullination

Citrullination is the conversion of peptidyl-arginine into the non-coded amino acid citrulline. Despite its importance in physiology and disease, global identification of citrullinated proteins and precise modification sites has remained challenging. Here, we employed quantitative mass spectrometry-based proteomics to generate a comprehensive atlas of citrullination sites in a physiologically relevant cell type. Collectively, we identified 14.056 citrullination sites within 4.008 proteins and quantified their regulation upon inhibition of the citrullinating enzyme PADI4. Using this rich dataset, we uncover general mechanistic and cell biological principles of citrullination function, while providing site-specific and quantitative information on thousands of PAD4 substrates within cells. Our findings include signature histone marks and numerous modifications on transcriptional regulators and chromatin-related signaling effectors. Additionally, we identify precise citrullination sites on an extensive list of known autoantigens. Collectively, we describe systems attributes of the human citrullinome and provide a resource framework for understanding citrullinaiton at the mechanistic level.

molecular biology↗

bioRxiv2021

The regulatory landscape of the human HPF1- and ARH3-dependent ADP-ribosylome

Despite the involvement of Poly(ADP-ribose) polymerase-1 (PARP1) in many important biological pathways, the target residues of PARP1-mediated ADP-ribosylation remain ambiguous. To explicate the ADP-ribosylation regulome, we analyzed human cells depleted for key regulators of PARP1 activity, histone PARylation factor 1 (HPF1) and ADP-ribosylhydrolase 3 (ARH3). Using quantitative proteomics, we quantified 1,596 ADPr sites, displaying a thousand-fold regulation across investigated knockout cells. We find that HPF1 and ARH3 inversely and homogenously regulate the serine ADP-ribosylome on a proteome-wide scale with consistent adherence to lysine-serine (KS)-motifs suggesting targeting is independent of HPF1 and ARH3. Our data reveal that ADPr globally exists as mono-ADP-ribosylation, and we detail a remarkable degree of histone co-modification with ADPr and other post-translational modifications. Strikingly, no HPF1-dependent target residue switch from serine to glutamate/aspartate was detectable in cells, which challenges current dogma related to PARP1 target residues. Collectively, we elucidate hitherto unappreciated processes related to cellular PARP1 activity.

molecular biology↗

bioRxiv2020

Mapping physiological ADP-ribosylation using Activated Ion Electron Transfer Dissociation (AI-ETD)

ADP-ribosylation (ADPr) is a post-translational modification that plays pivotal roles in a wide range of cellular processes. Mass spectrometry (MS)-based analysis of ADPr under physiological conditions, without relying on genetic or chemical perturbation, has been hindered by technical limitations. Here, we describe the applicability of Activated Ion Electron Transfer Dissociation (AI-ETD) for MS-based proteomics analysis of physiological ADPr using our unbiased Af1521 enrichment strategy. To benchmark AI-ETD, we profiled 9,000 ADPr peptides mapping to >5,000 unique ADPr sites from a limited number of cells exposed to oxidative stress, corresponding to 120% and 28% more ADPr peptides compared to contemporary strategies using ETD and EThcD, respectively. Under physiological conditions AI-ETD identified 450 ADPr sites on low-abundant proteins, including in vivo cysteine auto-modifications on PARP8 and tyrosine auto-modifications on PARP14, hinting at specialist enzymatic functions for these enzymes. Collectively, our data provides new insights into the physiological regulation of ADP-ribosylation.

molecular biology↗