The results will be published online Aug. 22 in the journals Nature, and Nature Structural and Molecular Biology. They open new possibilities for understanding, diagnosing and perhaps treating breast cancer.
BRCA2 is known to be involved in repairing damaged DNA, but exactly how it works with other molecules to repair DNA has been unclear, said Stephen Kowalczykowski, distinguished professor of microbiology in the UC Davis College of Biological Sciences, UC Davis Cancer Center member and senior author of the Nature paper.
"Having the purified protein makes possible far more detailed studies of how it works," Kowalczykowski said.
Kowalczykowski's group has purified the protein from human cells; another group led by Professor Wolf-Dietrich Heyer, also in the UC Davis Department of Microbiology and leader of the Cancer Center's molecular oncology program, used genetic engineering techniques to manufacture the human protein in yeast. That work is published in Nature Structural and Molecular Biology.
The two approaches are complementary, Heyer said, and the two teams have been talking and cooperating throughout.
"It's nice to be able to compare the two and see no disagreements between the results," Heyer said.
Experiments with the BRCA2 protein confirm that it plays a role in repairing damaged DNA. It acts as a mediator, helping another protein, RAD51, to associate with a single strand of DNA and stimulating its activity. One BRCA2 molecule can bind up to six molecules of RAD51.
The RAD51/DNA complex then looks for the matching strand of DNA from the other chromosome to make an exact repair.
If the BRCA2/RAD51 DNA repair system is not working, the cell resorts to other, more error-prone methods.
"It's at the apex of the regulatory scheme of DNA repair," Kowalczykowski said. Your DNA is constantly suffering damage, even if you avoid exposure to carcinogens. If that damage is not repaired, errors start to accumulate, Kowalczykowski said. Those errors can eventually lead to cancer.
The BRCA2 gene was discovered in 1994. Mutations in BRCA2 are associated with about half of all cases of familial breast and ovarian cancer (cases where the propensity to develop cancer seems to be hereditary), and are the basis for genetic tests.
But purifying the protein made by the gene has proved difficult.
"It's very large, it does not express well, and it degrades easily," Kowalczykowski said.
Ryan Jensen, a postdoctoral researcher in Kowalczykowski's lab, after testing many different cell lines, succeeded in introducing a BRCA2 gene into a human cell line and expressing (producing) it as a whole protein. Jensen and another postdoc, Aura Carreira, tested the purified protein for its function in repairing damaged DNA.
Jie Liu, a postdoctoral researcher in Heyer's lab, found that a much smaller protein called DSS1 stimulated BRCA2 to assemble functional RAD51/DNA complexes. Together with Liu, staff research associate Tammy Doty and UC Davis undergraduate student Bryan Gibson (now a doctoral student at Cornell University) purified the human BRCA2 and DSS1 proteins from yeast.
One application of the purified protein would be to make antibodies to BRCA2 that could be used in test kits as a supplement to existing genetic tests, Kowalczykowski said.
A more exciting possibility, he said, would be to use the system to screen for drugs that activate or inhibit the interaction between BRCA2, RAD51 and DNA. Many cancer treatments work by creating breaks in DNA, and a drug that selectively shuts down a specific DNA repair pathway -- making it harder for cancer cells to recover -- could make the cells more vulnerable to treatment. That strategy is already being exploited by a new class of drugs called PARP inhibitors, currently in clinical trials. PARP inhibitors target an alternate DNA repair pathway that cells use when the BRCA2 repair pathway is not available.
The BRCA2 protein can also be used to study how different mutations affect the gene's function.
"We're just starting to scratch the surface and understand more of the mechanisms and interaction with other factors," Kowalczykowski said.
The work was supported by grants from the National Institutes of Health, the U.S. Department of Defense Breast Cancer Research Program, the Susan G. Komen Breast Cancer Foundation, and the UC Davis Cancer Center. Jensen was supported by a fellowship from the American Cancer Society; Carreira was supported by a fellowship from the Spanish Ministry of Education and Science, and Liu by a fellowship from the Tobacco-Related Disease Research Program.
About the UC Davis Cancer Center
UC Davis Cancer Center is the only National Cancer Institute-designated center serving the Central Valley and inland Northern California, a region of more than 6 million people. Its specialists provide compassionate, comprehensive care for more than 9,000 adults and children every year, and offer patients access to more than 150 clinical trials at any given time. Its innovative research program includes more than 280 scientists at UC Davis and Lawrence Livermore National Laboratory. The unique partnership, the first between a major cancer center and national laboratory, has resulted in the discovery of new tools to diagnose and treat cancer. For more information, visit www.ucdmc.ucdavis.edu/cancer.
About the College of Biological Sciences
The Department of Microbiology is one of five departments in the UC Davis College of Biological Sciences, one of few colleges in the country dedicated entirely to the study of basic biology. The college's faculty, researchers and students are advancing the planet's knowledge on many frontiers by exploring fundamental questions about life.
About UC Davis
For more than 100 years, UC Davis has engaged in teaching, research and public service that matter to California and transform the world. Located close to the state capital, UC Davis has 32,000 students, an annual research budget that exceeds $600 million, a comprehensive health system and 13 specialized research centers. The university offers interdisciplinary graduate study and more than 100 undergraduate majors in four colleges -- Agricultural and Environmental Sciences, Biological Sciences, Engineering, and Letters and Science. It also houses six professional schools -- Education, Law, Management, Medicine, Veterinary Medicine and the Betty Irene Moore School of Nursing.
Stephen Kowalczykowski, Microbiology, (530) 752-5938, email@example.com
Wolf Heyer, Molecular and Cellular Biology, (530) 752-3001, firstname.lastname@example.org
Andy Fell, UC Davis News Service, (530) 752-4533, email@example.com
Dorsey Griffith, UC Davis Cancer Center, (916) 734-9118, Dorsey.Griffith@ucdmc.ucdavis.edu
Andy Fell | EurekAlert!
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences