How your immune system fires off electrons to repair DNA damage

Scientists have found out how a famous sunburn-healing enzyme works. The way it zaps DNA damage sounds so science fictional that it seems like something that happened a long time ago, in a galaxy far, far away.

Sunburn does a lot of damage to skin. Sometimes the skin is just roughened or splotched. Sometimes the damage develops into full-blown tumors. Although melanoma is easily treatable if caught early, its prevalence has been rising since the seventies. The tumors are caused by solar radiation, which causes the strands of DNA in a person's cells to jiggle fast enough that the atoms re-order themselves. These re-ordered parts are called dimers, and they can cause the cells in which they reside to replicate out of control, forming tumors.

One regular offender is the cyclobutane pyrimidine dimer. It's a bulbous ring attached to the elegant double helix of the DNA strand. It latches on to the damaged parts of DNA and is replicated along with them, causing widespread damage. Once it gets started, it can grow until it takes over the system.

How your immune system fires off electrons to repair DNA damage

Fortunately, help is on the way, in the form of an enzyme called photolyase. Photolyase floats around the body, looking for encroachment from the dark side. This enzyme powers itself up using blue light, and then shoots out an electron. Scientists once thought it shot out a beam of electrons that repaired all cell damage at once. Turns out, only one, damage-seeking electron (probably guided by the Force) is all it takes. The electron takes a route along the ring of photo-lesion, and blasts away the places where undesirable bonds have been formed. Homegrown resistance speeds it along its way. A molecule in the ring allows the electron to move faster along the ring than it could by hoping through the gap in the middle. The whole process takes less than a hundred trillionths of a second, and when the photolyase hits all the right spots with its electron, the ring is blasted away and the DNA repairs itself to form a perfect strand.

Ah, but there's a problem. Photolyase runs through fish and reptilian systems, but is unknown in mammals. Scientists are now trying to find a way to synthesize and mass-produce this enzyme, so that one day we might be able to repair our DNA with a simple lotion.

Via Ohio State University, soon to be published in Proceedings of the National Academy of Sciences.

Image: Erin O'Connor