More than half of the human genome is made up of bits of mobile DNA, which can travel inside the body and insert genes into the chromosomes of target cells. This DNA doctoring not only shapes species over time, it also spreads antibiotic resistance and is used by bacteria that spread Lyme disease and by viruses linked to certain forms of cancer.
Last year in Nature, scientists working in the Brown University lab of Arthur Landy and the Harvard Medical School lab of Thomas Ellenberger announced they had solved the structure of ë-integrase (ë-Int), the protein “surgeon” that allows mobile DNA to cut into a chromosome, insert its own genes, and then sew the chromosome back up. That work was conducted using the lambda virus, which infects Escherichia coli (E. coli) bacteria and serves as a model that scientists use to understand mobile DNA.
Now scientists in the Landy lab have solved the structure of a DNA-protein complex that acts as a team of “nurses,” aiding ë-Int during this snip-and-solder procedure known as site-specific recombination. The structure is a three-dimensional representation of the DNA within this complex. Pictured on the cover of the Nov. 17, 2006, journal Molecular Cell, it looks like DNA dressed for a party, a double helix decked with clumps of curly, colorful ribbon. By solving this structure, scientists now know how these six proteins interact with each other and fold DNA during site-specific recombination.
“Once you know how these proteins and DNA are arranged, you have a much better sense of their function,” said Xingmin Sun, a postdoctoral research associate in the Landy lab and the lead author of the journal article. “And once you know their function, you begin to see how the real work inside cells gets done.”
Sun said solving the structure of the DNA-protein complex called for some creativity. Because it is a string of six proteins, the complex is too big and too flexible to analyze through standard methods such as X-ray crystallography.
Sun used fluorescence resonance energy transfer or FRET, a technique typically used to study small protein complexes in a solution. This time, Sun used FRET to study large protein complexes in a gel. He tagged the DNA with fluorescent dyes and purified the proteins, placing them in a gel that was then shot through with light. Sun measured the wavelengths of light as they bounced between the molecules of dye. Those measurements were then fed into a special software program created by Dale Mierke, a Brown professor of medical science, which plotted their positions to create the structural map.
“The real breakthrough here is successfully using FRET to determine the structure of a large protein-DNA complex,” Sun said. “Biologists now have a new tool to help them understand a variety of these complexes, including ones that control cell division, gene expression and DNA replication. So this technique represents a big advance.”
Former Brown postdoctoral research associates Marta Radman-Livaja and Sang Yeol Lee were part of the research team, along with Tapan Biswas, a former postdoctoral research associate at Harvard Medical School. Landy, a professor of medical science in Brown’s Department of Molecular Biology, Cell Biology and Biochemistry, acted as senior scientist on the project.
The National Institute of General Medical Sciences supported the work.
Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews and maintains an ISDN line for radio interviews. For more information, call the Office of Media Relations at (401) 863-2476.
Wendy Lawton | EurekAlert!
New way to look at cell membranes could change the way we study disease
19.11.2018 | University of Oxford
Controlling organ growth with light
19.11.2018 | European Molecular Biology Laboratory
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure
Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...
19.11.2018 | Event News
09.11.2018 | Event News
06.11.2018 | Event News
19.11.2018 | Materials Sciences
19.11.2018 | Information Technology
19.11.2018 | Life Sciences