When DNA breaks, cells often repair it through a process called homologous recombination, in which a matching (replicated) copy of the broken sequence is used as a repair template. 2/n

Homologous recombination is key for protecting the genome, but it’s also challenging because the broken DNA must find its matching copy within billions of nucleotides. How can a cell achieve this? This is known as the “homology search” problem. 3/n

Now, after DNA replicates, sister chromatids are held together approx every 1 Mb so the search is confined to ~1 M nucleotides. But finding the right match is still a huge challenge – especially if the sisters aren’t perfectly aligned. 4/n

Simply relying on random 3D diffusion – letting the broken DNA wander through the nucleus – would be inefficient. Even for a 1 Mb region, the broken DNA would take far too long to find its matching sequence by chance alone. 5/n

We discovered that instead of searching randomly, cells use an active 1D scanning process: the repair machinery leverages a looping protein called cohesin to ‘slide’ the break along the DNA and find the matching sequence. 6/n

Thus, chromatin loops don’t just organize the genome to control gene expression – they also protect its integrity by helping a broken DNA find its matching sequence for repair! 7/n

Link to the publication below! Also check out the related study by Teloni et al from and the insightful perspective by Jiazhi Hu, all in the same issue. 8/n

Big thanks to our amazing team – especially co-first authors Adam and Namrata who put so much work into this project. It’s been a huge privilege to work with you. 9/n

Last but not least, I am incredibly grateful to my mentor, @taekjip, for giving me the freedom to take risks and for guiding me throughout the project. And co-mentor, Ralph Scully, for all his support and mentorship. 10/n