Circular ecDNA promotes accessible chromatin and high oncogene expression.

Area of Science:

• Cancer Biology
• Genomics
• Epigenetics

Background:

• Oncogenes are frequently amplified on extrachromosomal DNA (ecDNA) in cancer.
• The structural organization and regulatory impact of ecDNA remain incompletely understood.

Purpose of the Study:

• To elucidate the structure of circular ecDNA.
• To investigate the relationship between ecDNA structure, chromatin state, and oncogene expression in cancer.

Main Methods:

• Integration of ultrastructural imaging, long-range optical mapping, and whole-genome sequencing analysis.
• Pan-cancer analysis of ecDNA-encoded oncogenes.
• Quantitative assessment of chromatin state and accessibility on ecDNA.

Main Results:

• Demonstrated the circular structure of ecDNA.
• Oncogenes on ecDNA exhibit high expression levels, correlating with increased copy number.
• ecDNA chromatin shows intact domains but reduced higher-order compaction and enhanced accessibility.
• ecDNA exhibits increased ultra-long-range interactions with active chromatin.

Conclusions:

• The unique structural and epigenetic features of ecDNA contribute to enhanced oncogene function in cancer.
• This work bridges ecDNA biology with cancer genomics and epigenetics, offering new insights into oncogene regulation.