Genetic Double-Agents Unmasked

Babraham Institute and Cancer Research UK scientists have discovered that certain enzymes with a key activity in the immune system may be important in stem-cell development, but may also work against us by contributing to the occurrence of cancer. A family of enzymes known as DNA deaminases beneficially mutates the genetic code of antibodies to improve their ability to recognise foreign bodies. The usual target for the enzymes’ activity is cytosine (C), one of the four building blocks of DNA, however this research has shown that the enzymes can also target another DNA component: methylcytosine (cytosine carrying a methyl chemical group). The discovery may help to explain how methylcytosine is removed from DNA in naturally-occurring situations, such as stem-cell development, but it also suggests a possible mechanism for the mutations that occur in up to one third of hereditary diseases and many cancers. Hence DNA deaminases may be acting as ‘double-agents’.