DNA fragility put into context

摘要

Agents that hinder DNA replication can often cause breaks at specific chromo-some regions commonly called fragile sites. Two questions have been hotly debated concerning these chromosome regions: why are they so sensitive to DNA damage; and how does damage to genes encompassing such sites affect the biology of the damaged cells? A paper by Letessier et al. on page 120 of this issue presents a rather simple, yet ele-gant, answer to the first of these questions. The authors also report that, surprisingly, the sensitivity of specific fragile sites within a cell depends on the tissue or organ from which the cell originates - a conclusion that may provide clues to the answer to the second question.