Agreed—it’s hard to quantify how often this occurs endogenously. Intron loss (Fig. 5), which captures this repair pathway at the endogenous level, reflects only a subset of mutagenic events. We assume that in most cases, the RT copies from pre-mRNA without leaving a detectable scar in the genome.

@hinashah.bsky.social @agnelsfeir.bsky.social

Our study highlights RNA as a direct template for DNA repair, revealing RT-DSBR as a previously unrecognized and potentially mutagenic pathway. Huge thanks to the incredible team who made this work possible! (5/5)
🔗 www.nature.com/articles/s41...
#GenomeInstability #DNARepair #RNA #CRISPR #DSB

But does RT-DSBR leave a trace? Yes! Analysis of cancer genomes (MSK-IMPACT & PCAWG) revealed whole intron deletions (WIDs)—a mutational signature consistent with RNA being used as a template during repair. (4/5)

CRISPR/Cas9 screens identified DNA polymerase ζ (Polζ) as essential for RT-DSBR. This translesion polymerase surprisingly acts as a reverse transcriptase—copying RNA into DNA right at break sites. (3/5)

Using fluorescent and sequencing-based assays, we show that RNA-containing oligos and even mRNA can serve as templates for DSB repair in human cells. But which enzyme enables this RNA-templated process? (2/5)

Huge thanks to the incredible team who made this work possible! 🙌

Check out the full preprint here: 🔗 doi.org/10.1101/2025...

#GenomeInstability #DNARepair #RNA #CRISPR #DSB #Genomics

@agnelsfeir.bsky.social @hinashah.bsky.social

🚀 This study highlights RNA as a direct template for genome repair, revealing RT-DSBR as a previously unrecognized repair pathway with potential mutagenic consequences in cancer. (7/)

🔬But does RT-DSBR leave a footprint in the genome? YES! We analyzed cancer genome datasets (MSK-IMPACT & PCAWG) and found whole intron deletions (WIDs)—a mutational signature of RT-DSBR. (6/)

🔥 CRISPR/Cas9 genetic screens identified DNA polymerase ζ (Polζ) as the key player in RT-DSBR. This translesion polymerase acts as a reverse transcriptase to copy RNA into DNA at break sites. (5/)

🧬 Using fluorescent and sequencing-based assays, we show that RNA-containing oligos and mRNA can act as templates for DSB repair in human cells. But which enzyme facilitates this process? (4/)

💥 DNA double-strand breaks (DSBs) are dangerous lesions that threaten genome integrity. While canonical repair pathways rely on DNA templates, we uncovered an alternative mechanism: RNA-templated DSB repair (RT-DSBR). (3/)

Excited to share our latest work from my postdoc in the Sfeir Lab 🔬, in collaboration with the Simon Powell Lab! 🤝 This project was driven by an incredible team, including the amazing Manisha and superstar Hina! ✨ (2/)

🧬 But does RT-DSBR leave a footprint in the genome? YES! We analyzed cancer genome datasets (MSK-IMPACT & PCAWG) and found whole intron deletions (WIDs)—a mutational signature of RT-DSBR. (6/)

🔥 CRISPR/Cas9 genetic screens identified DNA polymerase ζ (Polζ) as the key player in RT-DSBR. This translesion polymerase acts as a reverse transcriptase to copy RNA into DNA at break sites. (5/)

🔬 Using fluorescent and sequencing-based assays, we show that RNA-containing oligos and mRNA can act as templates for DSB repair in human cells. But which enzyme facilitates this process? (4/)

💥 DNA double-strand breaks (DSBs) are dangerous lesions that threaten genome integrity. While canonical repair pathways rely on DNA templates, we uncovered an alternative mechanism: RNA-templated DSB repair (RT-DSBR). (3/)

Excited to share our latest work from my postdoc in the Sfeir Lab 🔬, in collaboration with the Simon Powell Lab! 🤝 This project was driven by an incredible team, including the amazing Manisha and superstar Hina! ✨ (2/)

I hear you, Helen, same here trying to prepare a grant. But we should get going. Science cannot stop!