Watching DNA Repair in Real Time

Sep 20, 2006

Direct observations of DNA are giving new insights into how genetic material is copied and repaired.

"We can monitor the process directly, and that gives us a different perspective," said Roberto Galletto, a postdoctoral scholar at UC Davis and first author on a paper published Sept. 20 on the Web site of the journal Nature.

In E. coli bacteria, molecules of an enzyme called RecA attach themselves along a DNA strand, stretching it out and forming a filament. A piece of complementary DNA lines up along side it, and pieces of DNA can be swapped in to repair gaps in the original strand. A similar protein, called Rad51, does the same job in humans.

"How RecA and Rad51 assemble into filaments determines the outcome of DNA repair, but very little is known about how assembly is controlled," said senior author Stephen Kowalczykowski, professor in the sections of Microbiology and of Molecular and Cellular Biology and director of the Center for Genetics and Development at UC Davis. Genes that control the human gene, Rad51, have been linked to increased risk of breast cancer.

Galletto attached a short piece of DNA to a tiny latex bead and placed it in a flow chamber, held by laser beam "tweezers." Fluid flowing past made the DNA stream out like a banner. Then he nudged it into an adjacent channel containing fluorescently-tagged RecA. After short intervals of time, he moved it back to the first chamber to observe the results.

By repeatedly dipping the same piece of DNA into the fluorescent channel, the researchers could see the RecA form clusters of four to five molecules on the DNA. Once those clusters had formed, the DNA/RecA filament rapidly grew in both directions. The measurements made in those experiments will be the baseline for future studies of both RecA and Rad51, Kowalczykowski said.

The new work adapts an approach developed by Kowalczykowski and Ronald J. Baskin, professor of molecular and cellular biology, to study single enzymes at work unwinding DNA strands. That research was first published in Nature in 2001.

Source: UC Davis

Explore further: Biologist reels in data to predict snook production

add to favorites email to friend print save as pdf

Related Stories

Team solves mystery associated with DNA repair

Dec 13, 2012

Every time a human or bacterial cell divides it first must copy its DNA. Specialized proteins unzip the intertwined DNA strands while others follow and build new strands, using the originals as templates. ...

Single-DNA images give clues to breast cancer

Oct 29, 2012

For the first time, researchers at the University of California, Davis, have watched single strands of DNA being prepped for repair. The research, published this week in the journal Nature, has implications for understanding the or ...

Study shows how DNA finds its match

Feb 08, 2012

It's been more than 50 years since James Watson and Francis Crick showed that DNA is a double helix of two strands that complement each other. But how does a short piece of DNA find its match, out of the millions ...

Recommended for you

Team advances genome editing technique

14 hours ago

Customized genome editing – the ability to edit desired DNA sequences to add, delete, activate or suppress specific genes – has major potential for application in medicine, biotechnology, food and agriculture.

User comments : 0