DNA repair is essential for cell vitality, cell survival and cancer prevention, yet cells' ability to patch up damaged DNA declines with age for reasons not fully understood.

Now, research led by scientists at Harvard Medical School reveals a critical step in a molecular chain of events that allows cells to mend their broken DNA.

The findings, published March 24 in Science, offer a critical insight into how and why the body's ability to fix DNA dwindles over time and point to a previously unknown role for the signaling molecule NAD as a key regulator of protein-to-protein interactions in DNA repair. NAD, identified a century ago, is already known for its role as a controller of cell-damaging oxidation.

Additionally, experiments conducted in mice show that treatment with the NAD precursor NMN mitigates age-related DNA damage and wards off DNA damage from radiation exposure.

The scientists caution that the effects of many therapeutic substances are often profoundly different in mice and humans owing to critical differences in biology. However, if affirmed in further animal studies and in humans, the findings can help pave the way to therapies that prevent DNA damage associated with aging and with cancer treatments that involve radiation exposure and some types of chemotherapy, which along with killing tumors can cause considerable DNA damage in healthy cells. Human trials with NMN are expected to begin within six months, the researchers said.

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