Sugar Code on Chromatin Drives Cellular Aging's Inflammatory Surge
A sugar modification on chromatin proteins orchestrates the gene program behind cellular senescence, revealing new targets to fight aging-related disease.
Summary
Researchers used a time-resolved chemical genomics approach to map how O-GlcNAc sugar modifications on chromatin proteins change during oncogene-induced senescence (OIS) in human fibroblasts. They found that chromatin O-GlcNAc levels accumulate progressively as cells become senescent, driven by rising OGT enzyme activity and falling OGA activity. Nearly 2,000 O-GlcNAc chromatin-associated proteins (OCPs) shift their genomic locations over time, forming two types of regulatory complexes: one that switches on inflammatory SASP genes (via TF–SWI/SNF) and another that silences cell-cycle genes (via NuRD). Two O-GlcNAcylated proteins, JUN and GATAD2A, were confirmed as key senescence regulators in both cell culture and animal tumor models, suggesting these modifications are actionable targets against aging and cancer.
Detailed Summary
Cellular senescence—the permanent exit of cells from the cell cycle—is a hallmark of aging and a driver of age-related diseases including cancer. While epigenetic changes are known to underpin the senescence transcriptional program, how O-GlcNAc (O-linked β-N-acetylglucosamine) modification of chromatin proteins coordinates this process has remained poorly understood.
This study employed a sophisticated time-resolved multiomics strategy in primary human fibroblasts undergoing oncogene-induced senescence (OIS). Using a chemical reporter system combined with proteomics and genome-wide chromatin mapping, the researchers tracked O-GlcNAc chromatin-associated proteins (OCPs) across six time points (Days 0–10). They also profiled the transcriptome and epigenome in parallel, enabling an integrated picture of how chromatin O-GlcNAc dynamics shape the senescence gene expression landscape.
Key findings reveal that total and chromatin-specific O-GlcNAc modification accumulates continuously during OIS, coinciding with upregulation of the O-GlcNAc transferase OGT and downregulation of the O-GlcNAc hydrolase OGA. Among 1,987 dynamically regulated OCPs, genomic occupancy shifts across diverse epigenetic chromatin states. These proteins display bimodal regulatory activity across the 3,466-gene senescence transcriptome. Mechanistically, O-GlcNAc facilitates formation of two distinct chromatin complexes: transcription factor–SWI/SNF complexes that activate SASP inflammatory genes at promoters, and NuRD complexes that silence cell-cycle regulators at enhancers—simultaneously enforcing both hallmarks of the senescent state.
Using both pharmacological tools (OGT inhibitor OSMI-4, OGA inhibitor Thiamet-G) and genetic approaches (shRNA knockdown, overexpression), the study validated that O-GlcNAc levels causally influence SA-β-Gal activity, proliferative arrest, and SASP gene expression. Critically, O-GlcNAcylated JUN (a key SASP transcription factor) and GATAD2A (a NuRD complex subunit) were identified as central regulators. Their roles were confirmed in in vivo xenograft and senescence-driven tumor models, where modulating these proteins altered tumor growth and senescence phenotypes.
These findings provide a mechanistic framework for how a single sugar modification integrates multiple epigenetic effectors into a coherent senescence program. They also suggest that targeting O-GlcNAc metabolism—particularly OGT activity or specific O-GlcNAcylated proteins like JUN and GATAD2A—could offer new therapeutic strategies for aging-associated inflammation, cancer, and other senescence-driven diseases.
Key Findings
- Chromatin O-GlcNAc modifications progressively accumulate during oncogene-induced senescence, driven by rising OGT and falling OGA levels.
- 1,987 O-GlcNAc chromatin proteins dynamically shift genomic occupancy, regulating 3,466 senescence-associated genes bidirectionally.
- TF–SWI/SNF complexes activate SASP inflammatory genes at promoters; NuRD complexes silence cell-cycle genes at enhancers.
- O-GlcNAcylated JUN drives SASP activation while O-GlcNAcylated GATAD2A enforces cell-cycle repression during senescence.
- Inhibiting OGT or targeting JUN/GATAD2A altered senescence phenotypes and tumor growth in both cell and animal models.
Methodology
Time-resolved chemical genomics combined proteomics with genome-wide chromatin mapping across six senescence time points in primary human fibroblasts using a doxycycline-inducible RAS-G12V OIS model. Parallel transcriptome and epigenome profiling enabled integrated multiomics analysis, validated by pharmacological OGT/OGA modulation and in vivo xenograft experiments.
Study Limitations
The study primarily uses an oncogene-induced senescence model, which may not fully recapitulate replicative or stress-induced senescence in vivo. Fibroblast-centric findings may not generalize to all cell types, and the clinical translatability of targeting specific O-GlcNAcylated sites on JUN or GATAD2A remains undemonstrated.
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