A repair enzyme crosses the border of the mitochondria to fix the main DNA of the cell.

The UNG1 enzyme was long considered a specialist protein that only handled maintenance for the small loop of DNA inside power-generating mitochondria. This discovery shows the enzyme regularly migrates to the cell nucleus to help repair the primary genetic code. This cross-border functionality means the cell has multiple layers of redundancy for protecting its most vital information. Before this, biology textbooks treated the mitochondria and the nucleus as mostly separate compartments with their own dedicated repair crews. Identifying this backup system helps explain how cells maintain their integrity during periods of high stress or aging.