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Updated: Jun 27, 2025
11:21
Author Spotlight: Advanced Single-Molecule Techniques for Investigating Telomeric Protein-DNA Interactions
Published on: August 30, 2024
709
Extrachromosomal telomere DNA derived from excessive strand displacements
Junyeop Lee1, Jina Lee1,2, Eric J Sohn1
1Institute for Cancer Genetics, Columbia University Vagelos College of Physicians and Surgeons, New York, NY 10032.
Summary
Alternative lengthening of telomeres (ALT) involves C-circles, unique to ALT cancers. This study reveals C-rich single-stranded DNAs (ssDNAs) are generated during Okazaki fragment processing, requiring specific protein complexes.
Area of Science:
- Molecular Biology
- Cancer Research
- Genetics
Background:
- Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism in ~15% of human cancers.
- ALT cancers feature extrachromosomal C-rich single-stranded DNAs (ssDNAs), including C-circles, but their origin is unknown.
Purpose of the Study:
- To define the generation process of C-rich ssDNAs and C-circles in ALT cells.
- To introduce a novel method for detecting single-stranded telomeric DNA.
Main Methods:
- Development and application of the 4SET (Strand-Specific Southern-blot for Single-stranded Extrachromosomal Telomeres) assay.
- Detection and characterization of C-rich ssDNAs and C-circles in cellular fractions.
Main Results:
- The 4SET assay detected C-rich ssDNAs (200-1500 nt) and C-circles in cytoplasm and nucleoplasm.
- C-rich ssDNAs originate during Okazaki fragment processing on the lagging strand.
- Generation involves CST-PP complex priming and DNA Polymerase delta/BLM helicase-mediated displacement synthesis.
Conclusions:
- Proposes a model for C-rich ssDNA and C-circle generation during ALT.
- Highlights the role of Okazaki fragment processing in ALT-associated DNA structures.
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