Dr Morris said: "Our findings showed that after DNA damage, SUMO becomes attached to BRCA1, switching it on and helping prevent breast cancer forming.

"We discovered how the cells in our body co-ordinate the difficult task of repairing potentially breast cancer causing DNA breaks and how they direct BRCA1 to do its job to stop tumours forming.

"This new insight is the first step towards developing drugs which may protect normal cells from the side effects of chemotherapy, or improve the effectiveness of current breast cancer treatments."

Dr Lesley Walker, Cancer Research UK's director of cancer information, said: "DNA damage, particularly double strand DNA breaks, are a fundamental cause of cancer and we know that people who have mutations in the BRCA1 gene have a higher risk of developing some kinds of cancer. Discovering that these 'limpet like' proteins play such an important role in repair may provide new opportunities to stop cancer from growing.

"But this is an extremely complex and intricate biological process so it may be many years before we can use this knowledge to safely intervene and help treat cancer patients."

Source: Cancer Research UK