Super-resolution microscopy in detecting DNA double strand breaks

New high-resolution microscopic technology has enabled researchers to make ground breaking discoveries about the role proteins have in homologous recombination, writes Rebecca Borg

Every day, our genetic makeup undergoes genomic stress and damage causing DNA double strands to weaken and break. This is a naturally occurring process that usually repairs itself through homologous recombination, one of the better pathways to repair the broken strands of DNA double helices.

“Homologous recombination is a process of DNA repair that a cell undertakes wherein thousands of different proteins come in and process, read, and communicate throughout the cell what's going on,” says Dr Donna Whelan, a DECRA Fellow and Academic in Pharmacy and Biomedical Science at La Trobe University. “Once a double-strand break has been identified, the end of the DNA is taken and the entire cell nucleus is searched for a very similar piece that can be used to fill in the gaps.”

When these “gaps” are not filled in correctly, a genetic mutation is likely to occur, leaving the host organism exposed to the development of numerous diseases, predominantly cancer.

“Double strand break resection through homologous recombination is the number one way of avoiding diseases, working 99.99 percent of the time. But when it doesn’t work it can be crucial towards impacting human health.”

Dr Whelan has observed the process of DNA double helix repair using several microscopic methods but she says the diffraction of light in conventional microscopy has a major blurring effect on proteins inside a cell that are only a few nanometres in size.

“By using biochemical methods as opposed to microscopic methods, you don’t get a lot of spatial and time information as you’re looking at multiple cells simultaneously,” Dr Whelan says. “And while microscopy is a powerful biology technique to see what’s happening inside of the cell within its natural environment, we haven’t been able to study the process in significant detail until now.”

Dr Whelan has been collaborating with her mentor, Associate Professor Eli Rothenberg of New York University, to develop new super-resolution microscopy methods. Their latest findings have been published in the Proceedings of the National Academy of Sciences (PNAS), and Professor Rothenberg believes it has led to a number of exciting developments in their field.

Dr Whelan is now analysing the precursors of double strand breaks and the appearance of stressed but unbroken replication forks in cells, in the hope that she can identify why some strands of damage can’t be repaired by the cell.

“Some of our recent findings were very unexpected, such as roles for proteins and certain interactions between proteins and outcomes,” says Dr Whelan. “It was unlooked for, but when we found it we had to go back and make sure it's real and to work out what it all means in the bigger picture, which really is the whole point of science.”