RaPID-seq– new paper published in Cell Reports
How does a cell find the right DNA template to accurately repair a DNA double-strand break?
When DNA breaks, cells can repair the damage through homologous recombination, a process that relies on RAD51 to search the genome for a matching DNA sequence from which missing genetic information can be copied. Despite its central role in maintaining genome stability, how RAD51 carries out this search within the complex three-dimensional environment of the human genome has remained difficult to study.
In our new work published in Cell Reports, Charles Yeh developed RAD51 proximity identification sequencing (RaPID-seq), a new approach that captures transient interactions made by RAD51 during the homology search. Together with colleagues, Charles used RaPID-seq to map where RAD51 searches for matching sequences following a DNA double-strand break in human cells.
The study reveals that homology search in humans is strongly constrained by spatial proximity: DNA regions that are physically close to the break are almost exclusively explored, highlighting an important role for the three-dimensional organization of chromatin in DNA repair. In contrast, homology search in yeast eventually expands globally to encompass the whole genome. This difference highlights a potential mechanism preventing erroneous recombination in humans between highly homologous, but spatially separated genes. We also found that externally introduced DNA repair templates, such as used in genome editing, can overcome these spatial constraints to efficiently participate in the repair process. Notably, these external DNA repair templates even interfere with native search and repair processes.
These findings provide a new view of how cells navigate the genome to accurately repair damaged DNA. Beyond improving our understanding of genome maintenance, the work may also help inform strategies to make homology-directed genome editing more efficient, predictable, and safe.
Congratulations to Charles and all collaborators on this exciting work!
For more info, read the paper in Cell Reports.
