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Updated: Aug 26, 2025
High-throughput Screening for Chemical Modulators of Post-transcriptionally Regulated Genes
Published on: March 3, 2015
High-throughput screen to identify compounds that prevent or target telomere loss in human cancer cells
Chris Wilson1, John P Murnane2
1Department of Pharmaceutical Chemistry, Small Molecule Discovery Center, University of California, San Francisco, CA 94143, USA.
Abstract:
Chromosome instability (CIN) is an early step in carcinogenesis that promotes tumor cell progression and resistance to therapy. Using plasmids integrated adjacent to telomeres, we have previously demonstrated that the sensitivity of subtelomeric regions to DNA double-strand breaks (DSBs) contributes to telomere loss and CIN in cancer. A high-throughput screen was created to identify compounds that affect telomere loss due to subtelomeric DSBs introduced by I-SceI endonuclease, as detected by cells expressing green fluorescent protein (GFP). A screen of a library of 1832 biologically-active compounds identified a variety of compounds that increase or decrease the number of GFP-positive cells following activation of I-SceI. A curated screen done in triplicate at various concentrations found that inhibition of classical nonhomologous end joining (C-NHEJ) increased DSB-induced telomere loss, demonstrating that C-NHEJ is functional in subtelomeric regions. Compounds that decreased DSB-induced telomere loss included inhibitors of mTOR, p38 and tankyrase, consistent with our earlier hypothesis that the sensitivity of subtelomeric regions to DSBs is a result of inappropriate resection during repair. Although this assay was also designed to identify compounds that selectively target cells experiencing telomere loss and/or chromosome instability, no compounds of this type were identified in the current screen.
Insights
This study identifies compounds affecting telomere loss and chromosome instability (CIN) by screening a library of biologically active molecules. Inhibition of DNA repair pathways like classical nonhomologous end joining (C-NHEJ) exacerbates telomere loss, while other compounds show protective effects.
Area of Science:
- Genetics and Genomics
- Cancer Biology
- Molecular Oncology
Background:
- Chromosome instability (CIN) is a hallmark of cancer, driving tumor progression and therapeutic resistance.
- Subtelomeric regions are sensitive to DNA double-strand breaks (DSBs), contributing to telomere loss and CIN.
- Previous work established a link between subtelomeric DSB sensitivity, telomere loss, and cancer development.
Purpose of the Study:
- To identify compounds that modulate telomere loss induced by subtelomeric DNA double-strand breaks (DSBs).
- To investigate the role of DNA repair pathways, specifically classical nonhomologous end joining (C-NHEJ), in subtelomeric DSB repair.
- To explore potential therapeutic strategies targeting CIN by identifying compounds that influence subtelomeric DSB repair dynamics.
Main Methods:
- A high-throughput screen using a reporter system (GFP) to detect telomere loss following I-SceI-induced DSBs in subtelomeric regions.
- Screening of a library of 1832 biologically-active compounds to identify modulators of DSB-induced telomere loss.
- Curated screening of hit compounds at various concentrations, including assessment of C-NHEJ inhibition and specific molecular targets (mTOR, p38, tankyrase).
Main Results:
- The screen identified compounds that either increase or decrease the frequency of GFP-positive cells (indicating telomere loss).
- Inhibition of C-NHEJ significantly increased DSB-induced telomere loss, confirming C-NHEJ's functional role in subtelomeric repair.
- Compounds decreasing telomere loss included inhibitors of mTOR, p38, and tankyrase, supporting the hypothesis of inappropriate resection during repair.
Conclusions:
- Classical nonhomologous end joining (C-NHEJ) plays a protective role in subtelomeric regions against DNA double-strand break-induced telomere loss.
- Inhibitors of mTOR, p38, and tankyrase may represent novel therapeutic avenues for managing chromosome instability in cancer.
- The current assay did not identify compounds that selectively target cells experiencing telomere loss or chromosome instability.
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