Scientists Map Out DNA Damage Caused by Cigarette Smoking

Researchers from the University of North Carolina's School of Medicine have developed a new method that's capable of mapping out DNA damage caused by cigarette smoking.

The new method, described in a paper published in the journal Proceedings of the National Academy of Sciences, could effectively map out sites on the human genome that are currently undergoing repair following a common type of DNA damage caused by a major chemical carcinogen known as benzo[α]pyrene (BaP).

"It would be good if this helps raise awareness of how harmful smoking can be," said Nobel laureate Aziz Sancar, MD, Ph.D., the Sarah Graham Kenan Professor of Biochemistry and Biophysics at UNC's School of Medicine, in a press release. "It also would be helpful to drug developers if we knew exactly how DNA damage is repaired throughout the entire genome."

BaP is a member of the so-called polycyclic aromatic hydrocarbons, which is a family of simple, hardy, carbon-rich hydrocarbons. It is commonly produced from everyday combustions, such as forest fires, diesel engines and even barbecue grills. These combustions send out BaP into land and air and is considered to be not very harmful to humans. However, cigarette smoking could produce BaP and directly deliver the toxic hydrocarbons to tissues.

When BaP enters the body, certain enzymes in the blood break it down to smaller, safer molecules. However, the protective reactions also yield a more destructive compound known as benzo[α]pyrene diol epoxide (BPDE), The BPDE compound can react chemically with DNA, forming a very tight bond at the nucleobase guanine. This damages the DNA, making it incapable of producing proteins properly. As a result, DNA can't be duplicated properly during cell division.

The body has its own way of handling damaged DNA. Dubbed as nucleotide excision repair, the body recruits a special type of protein that's capable of snipping out the damaged strand of DNA. The snipped out DNA bits free floats until certain molecules finally degrade it.

Using the new method, the researchers were able to collect these free-floating snippets of DNA. Like pieces of a giant puzzle, the researchers sequenced the DNA snippets and fit it to their sequences. By doing so, the researchers created a complete map of the sites where the repair of the damaged DNA was done.

With the positive result of their study, the researchers claim that their new method can also be used DNA damage caused by other environmental toxins.