Biology subjects

Oliviero, G.

Publications and source records attributed to Oliviero, G..

6 recordsLinked to original sources

bioRxiv2026

SS18-SSX co-opts P300 to sustain oncogenic transcription independent of SWI/SNF activity

Synovial sarcoma is driven by the SS18-SSX fusion oncoprotein, which has been assumed to promote tumorigenesis through its incorporation into the SWI/SNF chromatin remodeling complexes. Accordingly, therapeutic efforts have focused on targeting SS18-SSX containing SWI/SNF assemblies, yet these approaches have produced limited clinical benefit. Here, we demonstrate that SS18-SSX sustains oncogenic transcription independent of SWI/SNF activity. Despite efficient degradation and dismantling of SWI/SNF complexes, fusion occupancy at target loci and associated gene expression programs remain largely intact. Instead, we identify the acetyltransferase P300 as an essential co-factor supporting SS18-SSX chromatin binding and transcriptional activation. Targeting P300 displaces the fusion from chromatin, suppresses its transcriptional output, compromising synovial sarcoma viability. Notably, dual PROTAC mediated degradation of P300 and SWI/SNF produces strong synergistic effects, broadly disrupting SS18-SSX localization and function. These findings redefine the mechanistic basis of synovial sarcoma and reveal a mechanistically anchored therapeutic strategy for targeting its core oncogenic driver.

cancer biology↗

bioRxiv2023

Specific cPRC1 complexes are co-opted to mediate oncogenic gene repression in diffuse midline glioma

Diffuse midline glioma (DMG) is a fatal childhood brain tumour characterised primarily by mutant histone H3 (H3K27M). H3K27M causes a global reduction in Polycomb Repressive Complex 2 (PRC2)-mediated H3K27me3 by inhibiting PRC2 enzymatic activity. Paradoxically, PRC2 is essential in DMG tumour cells where residual complex activity is required for oncogenic gene repression, although the molecular mechanisms acting downstream of PRC2 in this context are poorly understood. Here, weve discovered this oncogenic gene repression is mediated by specific canonical PRC1 (cPRC1) formations. By combining CRISPR screening, biochemical and chromatin mapping approaches with functional perturbations we show that cPRC1 complexes containing CBX4 and PCGF4 drive oncogenic gene repression downstream of H3K27me3 in DMG cells. Remarkably, the altered H3K27me3 modification landscape characteristic of these tumours rewires the distribution of cPRC1 complexes on chromatin. CBX4 and PCGF4 containing cPRC1 accumulate at sites of H3K27me3 while other cPRC1 formations are displaced. Despite accounting for <5% of cPRC1 complexes in DMG, CBX4/PCGF4-containing complexes predominate as gene repressors. Our findings link the altered distribution of H3K27me3 with imbalanced cPRC1 function, promoting oncogenic gene repression in DMG cells, revealing new disease mechanisms and highlighting potential therapeutic opportunities in this incurable childhood brain tumour.

cancer biology↗

bioRxiv2023

Loss of Polycomb Repressive Complex 2 function causes asparaginase resistance in T-acute lymphoblastic leukemia through decreased WNT pathway activity

Loss-of-function mutations and deletions in core components of the epigenetic Polycomb Repressive Complex 2 (PRC2) are associated with poor prognosis and treatment resistance in T-acute lymphoblastic leukemia (T-ALL). We leveraged clinical mutational and transcriptional data to identify a functional link between PRC2 alterations and changes in WNT signaling pathway activity in leukemia cells. Computational integration of transcriptomic, proteomic and phosphoproteomic data from an isogenic T-ALL cellular model revealed reduced activity of the WNT-dependent stabilization of proteins (WNT/STOP) pathway in cells lacking core PRC2 factor EZH2. We discovered that PRC2 loss significantly reduced sensitivity to key T-ALL treatment asparaginase, and that this was mechanistically linked to increased cellular ubiquitination levels that bolstered leukemia cell asparagine reserves. We further found that asparaginase resistance in PRC2-depleted leukemic blasts could be mitigated by pharmaceutical proteasome inhibition, thereby providing a novel and clinically tractable means to tackle induction treatment failure in high-risk T-ALL.

cancer biology↗

bioRxiv2022

Analysis of context-specific KRAS-effectors (sub)complexes in Caco-2 cells

Ras is a key switch controlling cell behavior. In the GTP-bound form, Ras interacts with numerous effectors in a mutually exclusive manner, where individual Ras-effectors are likely part of larger cellular (sub)complexes. The molecular details of these (sub)complexes and their alteration in specific contexts is not understood. Focusing on KRAS, we performed affinity purification (AP)-mass spectrometry (MS) experiments of exogenous expressed FLAG-KRAS WT and three oncogenic mutants ( genetic contexts) in the human Caco-2 cell line, each exposed to 11 different culture media ( culture contexts) that mimic conditions relevant in the colon and colorectal cancer. We identified four effectors present in complex with KRAS in all genetic and growth contexts ( context-general effectors). Seven effectors are found in KRAS complexes in only some contexts ( context-specific effectors). Analyzing all interactors in complex with KRAS per condition, we find that the culture contexts had a larger impact on interaction rewiring than genetic contexts. We investigated how changes in the interactome impact functional outcomes and created a shiny app for interactive visualization. We validated some of the functional differences in metabolism and proliferation. Finally, we used networks to evaluate how KRAS effectors are involved in the modulation of functions by random walk analyses of effector-mediated (sub)complexes. Altogether, our work shows the impact of environmental contexts on network rewiring, which provides insights into tissue-specific signaling mechanisms. This may also explain why KRAS oncogenic mutants may be causing cancer only in specific tissues despite KRAS being expressed in most cells and tissues.

systems biology↗

bioRxiv2022

Interplay between Polycomb PCGF protein interactomes revealed by screening under endogenous conditions

The six PCGF proteins (PCGF1-6) define the biochemical identity of Polycomb Repressor Complex 1 (PRC1) subcomplexes. While structural and functional studies of PRC1 subcomplexes have revealed specialized roles in distinct aspects of epigenetic regulation, our understanding of variation in protein interaction networks between the PCGF subunits is incomplete. We carried out an affinity purification mass spectrometry (AP-MS) screen of subunits PCGF1 (NSPC1), PCGF2 (MEL18), and PCGF4 (BMI1), using an immunoprecipitation approach that replicated endogenous cellular conditions in a cell line capable of differentiation programs. Over 200 interactions were found, including 83 that had not been described previously. Bioinformatic analysis found that these interacting proteins covered a range of functional pathways, often focused on cell biology and chromatin regulation. We found evidence of mutual regulation (at mRNA and protein level) between distinct PCGF subunits. Furthermore, we confirmed that disruption of each subunit using shRNA results in reduced proliferation ability. Overall, our work adds to understanding of the role of PCGF proteins within the wider cellular network.

cancer biology↗

bioRxiv2021

Distinct and diverse chromatin-proteomes of ageing mouse organs reveal protein signatures that correlate with physiological functions

Temporal molecular changes in ageing mammalian organs are of relevance to disease etiology because many age-related diseases are linked to changes in the transcriptional and epigenetic machinery that regulate gene expression. We performed quantitative proteome analysis of chromatin-enriched protein extracts to investigate the dynamics of the chromatin-proteomes of the mouse brain, heart, lung, kidney, liver, and spleen at 3, 5, 10, and 15 months of age. Each organ exhibited a distinct chromatin-proteome and sets of unique proteins. The brain and spleen chromatin-proteomes were the most extensive, diverse, and heterogenous among the six organs. The spleen chromatin proteome appeared static during the lifespan, presenting a young phenotype that reflects the permanent alertness state and important role of this organ in physiological defense and immunity. We identified a total of 5928 proteins, including 2472 nuclear or chromatin associated proteins across the six mouse organs. Up to 3125 proteins were quantified in each organ demonstrating distinct and organ-specific temporal protein expression timelines and regulation at the post-translational level. Bioinformatics meta- analysis of these chromatin proteomes revealed distinct physiological and ageing- related features for each organ. Our results demonstrate the efficiency of organelle specific proteomics for in vivo studies of a model organism and consolidate the hypothesis that chromatin-associated proteins are involved in distinct and specific physiological functions in ageing organs. HIGHLIGHTSO_LIQuantitative chromatin-proteome analysis during mouse lifespan; C_LIO_LIChromatin analysis in vitro and in vivo mouse models; C_LIO_LIDistinct chromatin proteomes of six organs during mouse lifespan; C_LIO_LICorrelations between ageing and chromatin regulation in mammalian lifespan. C_LI

cell biology↗