Our DNA becomes more damaged as we age and some scientists believe that this causes ageing. We have inbuilt DNA repair systems in every cell, but these systems can break down as we age leading to increased DNA damage. Mutations in genes responsible for DNA repair can cause premature ageing like in Werner’s Disease. So up until now DNA damage has been seen to be a bad thing. Now a new study shows that DNA breaks in neurons (brain cells) actually helps us form memories.
A set of genes called early response genes must be turned on in neurons for us to be able to learn and create new memories. When we are not forming new memories, several proteins, including one called Topo IIb, sit on the promoter regions of the early response genes and stop these genes from being turned on. The promoter region is an area just before a gene that contains a start signal and allows that gene to be transcribed into RNA and then turned into protein.
When we are learning or creating a new memory, Topo IIb causes breaks in the promoter region of early response genes. When this happens the proteins that normally sit on the promoter region of the early response genes move away and the genes can be turned on or transcribed. This happens very quickly – within 30 minutes. The cell then works to repair the DNA breaks which happens after about 2 hours. When the breaks are repaired, the early response genes are turned off again. If DNA repair is inhibited, the early response genes stay turned on for longer. It isn’t yet clear whether this would be a good or a bad thing.
DNA repair systems deteriorate as we age. There is also more damage in aged brain cells and older people are more likely to have memory loss and problems learning and forming new memories. However, more work will need to be done to see whether this is because of changes in how DNA breaks are repaired in neurons.
This study is cool because it shows that DNA damage is not always a bad thing. It also shows how complex our DNA is and how much more we have to learn about how it works
The Scientific Paper: