RNA Transcripts Serve as a Template for Double-Strand Break Repair in Human Cells.

Area of Science:

• Molecular Biology
• Genetics
• Genomics

Background:

• Double-strand breaks (DSBs) are critical DNA lesions that compromise genome stability.
• Canonical DNA repair pathways typically do not involve RNA, but recent findings suggest RNA's potential influence on repair outcomes.
• The direct role of transcript RNA as a template in human cellular DSB repair remains largely uncharacterized.

Purpose of the Study:

• To investigate the direct role of RNA as a template in double-strand break repair in human cells.
• To identify factors and mechanisms governing RNA-templated DNA repair (RT-DSBR).
• To explore the genomic consequences of RT-DSBR in cancer.

Main Methods:

• Development of fluorescent and sequencing-based assays to detect RNA-templated repair.
• CRISPR/Cas9-based genetic screening to identify key factors in RT-DSBR.
• Bioinformatic analysis of cancer genome sequencing data.

Main Results:

• Demonstrated that RNA oligonucleotides and messenger RNA can serve as templates to promote DSB repair.
• Identified DNA polymerase-zeta (Polζ) as a key enzyme, potentially acting as a reverse transcriptase, that facilitates RT-DSBR.
• Discovered whole intron deletions in cancer genomes as a distinct genomic scar indicative of RT-DSBR using spliced mRNA.

Conclusions:

• RNA-templated DNA repair (RT-DSBR) is an alternative pathway for repairing DSBs within transcribed genes.
• RT-DSBR involves Polζ and can lead to specific mutagenic outcomes, such as intron deletions.
• The findings reveal a novel mechanism of DNA repair with implications for genome stability and cancer mutagenesis.