Mitotic transcription ensures ecDNA inheritance through chromosomal tethering

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Extrachromosomal DNA (ecDNA) are circular DNA molecules frequently found in cancer cells.
• ecDNA contribute to tumor progression and drug resistance by amplifying oncogenes.
• The inheritance mechanisms of ecDNA are not well understood, despite their importance.

Purpose of the Study:

• To investigate the mechanisms governing the faithful inheritance of extrachromosomal DNA during cell division.
• To elucidate how ecDNA avoid mis-segregation and maintain high copy numbers in cancer cells.

Main Methods:

• Utilized cancer cell lines with ecDNA, including those co-amplifying MYC and PVT1.
• Employed BRD4 inhibition, PVT1 depletion, and mitotic transcription inhibition.
• Observed ecDNA localization, cytosolic mis-segregation, and chromosomal integration using microscopy and genetic analyses.

Main Results:

• ecDNA are protected from cytosolic mis-segregation by clustering and tethering to mitotic chromosomes.
• This tethering is dependent on BRD4 and the long non-coding RNA PVT1.
• Disrupting this tethering leads to ecDNA mis-segregation, integration, and homogeneously staining regions (HSRs).

Conclusions:

• A novel RNA-mediated tethering mechanism facilitates nuclear inheritance of ecDNA.
• This mechanism links ecDNA to mitotic chromosomes, preventing cytosolic loss and integration.
• Understanding ecDNA inheritance is crucial for developing targeted cancer therapies.