Joint lead author Dr Gerald Pao, from the Salk Institute for Biological Studies, La Jolla, California, and colleagues say that the lack of, or mutation in, BRCA1 leads to activation of normally silent DNA, which causes cells not to repair properly, divide haphazardly and can lead to chromosomal abnormalities, all of which can cause cancer.
Blood tests that can detect the RNA of this normally silent, so-called 'junk DNA' could help doctors detect breast cancer, particularly among younger women whose firm, healthy breast tissue can disguise tumours on ultrasound scans, explained Dr Pao.
Co-author on the study, Professor Inder Verma, said that: 'The issue of what BRCA1 does has been marred in controversy because people kept finding it everywhere, and there was no consistent picture of what it was doing'.
He added: 'We hope this study now provides a new cohesive direction for BRCA1 research so that we can answer the fundamental questions about how this gene promotes cancer and how we might be able to improve early diagnosis and, possibly, treat BRCA1-induced cancer more effectively'.
Over 230,000 women in the USA are diagnosed with breast cancer annually, and almost 10 percent of them will have mutations in either BRCA1 or BRCA2.
The team made their discovery during a study involving mice that had their copy of the BRCA1 gene 'knocked-out'. The DNA in the cells of these mice was not 'packaged' correctly. 'Every chromosome is packaged into chromatin, and within this chromatin there is heterochromatin, which is even further condensed in order to ensure the genes within are really silent', said Dr Pao.
While the findings indicate what a loss or mutation of BRCA1 could lead to, they do not show conclusively how the loose packaging of such DNA actually causes cell mutation and tumour development.