Yeast Enzyme Repairs DNA Breaks Caused by Bleomycin

Moore and colleagues, writing in the Journal of Bacteriology in 1988, studied how yeast cells repair DNA damage caused by bleomycin, a chemotherapy drug that cuts DNA strands. The work focused on an enzyme called polydeoxyribonucleotide ligase, which rejoins broken DNA strands by linking fragments of genetic material back together.

The researchers compared two types of baker's yeast (Saccharomyces cerevisiae): one with a working copy of the ligase gene (CDC9) and one lacking it (cdc9). Cells with functioning ligase eliminated about 90% of the DNA breaks caused by bleomycin within 90 to 120 minutes of treatment. Cells without the enzyme could not rejoin these breaks at all. The experiments used doses of bleomycin calibrated either to produce equal numbers of DNA breaks or equal amounts of cell death, and examined how the enzyme deals with unusual chemical ends on the broken DNA, called 3'-phosphoglycolate termini, that bleomycin leaves behind.

This is a study of basic yeast cell biology and enzymology, not of skin, wound healing, or any human application. It shows how one organism's repair machinery handles chemically damaged DNA, but says nothing about DNA fragments as a topical or injected material, and nothing about human tissue or cells.