Work led by Francis Crick Institute scientists has improved our
understanding of homologous recombination - an essential process
for repairing broken DNA that could otherwise lead to cancer.
Simon Boulton of the Crick explains: "Our work provides
mechanistic insight into homologous recombination, which is an
essential mechanism for the repair of double-stranded breaks in DNA
and damaged replication forks. Failure to carry out homologous
recombination is associated with cancer predisposition."
Last year Dr Boulton's team published a paper in Celldescribing the biochemical function of an important family of
tumour suppressor proteins called Rad51 paralogs. When they're
mutated in humans, these proteins cause hereditary breast and
ovarian cancer and Fanconi anemia - a genetic disease that causes
bone marrow failure and cancer in most sufferers, among other
problems.
In their 2016 paper, the researchers extended their study of
Rad51 paralogs using cutting-edge science to show precisely how the
proteins modulate Rad51-DNA filaments to repair breaks.
Specifically, the team used a technique called stopped-flow
kinetic measurements to study the formation and stability of Rad51
filaments and a method called single-molecule fluorescence
resonance energy transfer (FRET) to monitor changes in filament
length and flexibility. Collaborator Eric Greene of Columbia
University Medical Center in New York pioneered DNA curtain
technology, which allowed the scientists to watch what happened to
Rad51 filaments when molecules of Rad51 paralogs were present.
Together the results revealed that the Rad51 paralogs keep Rad51
bound to DNA strands by capping the ends of the Rad51-DNA filaments
and keeping them stable.
The next step for researchers is carrying out structural studies
of the process.
Dr Boulton says: "Targeting this process with small molecules
that interfere with it could provide a way to prevent homologous
recombination and thus sensitise cells to agents that damage DNA.
This might be something we could exploit in cancer treatments - it
could provide a way to stop DNA repair in cancerous cells and
therefore stop these growing and replicating."
The paper, A Polar and Nucleotide-Dependent Mechanism of
Action for RAD51 Paralogs in RAD51 Filament Remodeling, is
published in Molecular Cell.