Every cell in our body constantly faces threats that can damage its DNA—this might be caused by environmental stress, chemical exposure, or even normal cellular processes. To keep their DNA intact, cells have evolved a wide range of repair systems. Fixing DNA damage properly is essential—not only for the survival of individual cells, but also for preventing diseases like cancer. What is often overlooked is that our DNA isn’t stored in one uniform environment. Inside the cell’s nucleus, DNA is packaged into different “neighborhoods,” known as chromatin domains. Some areas are loosely packed and easy to access (called euchromatin), while others are tightly condensed and more difficult to reach (called heterochromatin). These differences in DNA packaging can influence how easily the repair systems find and fix DNA damage. In this project, we wanted to understand how these different DNA neighborhoods—especially the densely packed heterochromatin—affect the way cells detect and repair broken DNA. We focused on two types of heterochromatin: one that is always tightly packed (called constitutive heterochromatin), and one that can change its structure depending on the cell's needs (called facultative heterochromatin). To study this, we used fruit flies, a powerful model system for genetic research. We developed precise tools that allow us to create controlled DNA damage in specific regions of the fly’s genome, and then watch in real time how the cell responds. By combining these tools with advanced imaging and molecular analysis, we discovered new ways in which cells change the structure of heterochromatin to help repair DNA damage more efficiently. Understanding how cells repair DNA in these tightly packed regions is not just important for basic science—it also has implications for human health. Similar processes are at work in human cells, and problems with DNA repair in heterochromatin may contribute to cancer development. Our findings could eventually help us understand how tumors resist treatment and how we might design better therapies in the future by targeting these repair mechanisms.
