Resilience by Improvisation

Our cells can copy DNA even when it is severely damaged. Prof. Zvi Livneh and Ph.D. student Ayelet Maor-Shoshani of the Biological Chemistry Department inserted a foreign material - similar to that making up crude oil - into the DNA of the bacterium E. coli. To their surprise, the cell’s copying machinery was able to proceed unhindered.

The millions of cells that divide every day in the body do so by copying their DNA. This crucially important function, which enables the body to replace old cells and pass on genetic information from generation to generation, is performed by molecules called DNA polymerases. The new Weizmann Institute study shows that they are able to improvise to achieve their goal.

The scientists found that upon reaching the foreign material, the DNA polymerase stops working and a specialized DNA polymerase jumps in to rescue the stuck replication process. The latter is able to continue the copying process by inserting “nonsense” genetic components into the copy, much like a singer who forgets a few words and continues to sing by making up new ones. In other cases, the specialized DNA polymerase simply skipped over the foreign material or deleted it and was thus able to continue copying as usual.

These findings, published in Proceedings of the National Academy of Sciences (PNAS), USA, shed light on how the copying process is affected by damaged DNA. “They show the remarkable capacity of a cell to reproduce,” says Livneh, “and make one hopeful that even if extreme types of chemicals are accidentally introduced into our DNA, the body will be able to manage.”