Handymen and not-so-handymen often reach for a roll of duct tape when they need to quickly, if temporarily, patch a leaky pipe or repair broken eyeglass frames.

And when it comes to certain types of DNA damage, cells turn to their own version of duct tape, an enzyme called DNA polymerase Q, or POL-Q.

The enzyme is by no means perfect when it makes its repairs, said molecular oncologist Richard Wood. In fact, it often makes mistakes ---- genetic mutations ---- that need to be corrected later. But POL-Q can rapidly fill in gaps in DNA or quickly replace damaged areas in the DNA strands, mistakes that otherwise would halt the process of DNA replication and virtually ensure the cell's death.

"You trade mutation for survival," said Wood, who heads the Molecular and Cellular Oncology Program at the University of Pittsburgh Cancer Institute.

Wood, research associate Mineaki Seki and colleagues at Pitt and Osaka University reported this newly discovered function of POL-Q in a paper published online last week by The EMBO Journal, a publication of the European Molecular Biology Organization.

POL-Q is one of 15 such enzymes that are involved in repairing the damage that occurs routinely in cellular DNA, the molecule that encodes genetic information. Failure to repair this damage, or mistakes made in repair, can lead to cancer.

While Wood's group has been characterizing the enzyme, a research team headed by John Schimenti, a geneticist at Cornell University, has developed a mouse without an active gene for producing POL-Q. Schimenti will report in an upcoming issue of the journal Molecular and Cellular Biology that these "knockout" mice had blood cells that were unusually susceptible to radiation damage.

These knockout mice didn't get cancer, Schimenti said, because they didn't live long enough for cancers to develop. But when knockout mice also were given a mutation that is known to cause cancer in mice, the combination proved lethal.

Wood emphasized that it's too soon to say where this basic research might lead. One implication, however, is that tumor cells might be more susceptible to radiation therapy if the POL-Q enzyme could be suppressed.