Some chromosomal locations, known as common fragile sites, are predisposed to breakage. These sites have pathogenic relevance as they are frequently associated with chromosomal translocations. Here, it is found that rather than breakage being due to replication stalling, the fragility of site FRA3B results from an unusually low density of replication origins in this region. Unexpectedly, fragility is found to be cell-type-specific, which may have implications for current models of translocations.
- Anne Letessier
- Gaël A. Millot
- Michelle Debatisse
