Scientists compress 10 million years of molecular evolution into 10 days Discovery expedites lab experiments

July 31, 1992|By Los Angeles Times

SAN DIEGO -- Scientists at Scripps Research Institute will announce today that they have discovered a process that can be used to compress 10 million years of molecular evolution into 10 days, thus expediting laboratory experiments.

The discovery, reported in today's issue of Science, offers insights into the process of evolution as well as providing possible new tools for genetic engineering, according to experts familiar with the study.

"This is closer to evolution than what anyone has done before," said Leslie Orgel, a chemist with the Salk Institute.

The Scripps scientists said their work -- in which they directed the evolution of a molecule in a test tube -- can be used someday to tailor specific molecules that could be used to help battle viral diseases, such as acquired immune deficiency syndrome.

"There are plenty of enzymes in nature that have evolved. Now it's happening, not in nature, but on our bench," said Gerald Joyce, an assistant professor of chemistry and molecular biology at Scripps Research Institute.

"It's just mimicking the process of Darwinian evolution and speeding it up to a large population of molecules," he said.

Mr. Joyce and Scripps research technician Amber Beaudry started with one population of enzymes, those that cleave RNA (ribonucleic acid), and forced them to evolve in 10 generations into a different type of enzyme, one that cleaves DNA (deoxyribonucleic acid).

Some scientists called the discovery a crucial step in the advancement of biotechnology.

"It's really important. It's the first time these new evolution methods have been used to change what an enzyme does," said Jack Szostak, professor of genetics at Harvard Medical School.

Mr. Joyce and Ms. Beaudry began their study with a population of 10 trillion molecules. They chose a particular group of molecules that usually cleave RNA, and that have a limited ability to cut strands of DNA under high temperatures.

Through a series of tests, the researchers pinpointed any individual molecules that were able to cleave DNA and gave them chemical markers.

The marked molecules were allowed to reproduce. With each generation, new mutations evolved.

After 10 generations, the researchers ended up with molecules that were 100 times more efficient at cleaving DNA than the originals, Mr. Joyce said. The evolved molecules could carry out the activity under normal cell-like conditions and didn't require high temperatures.

The ability to snip strands of a cell's DNA is a useful one because in doing so, the molecule has stopped the cell's ability to reproduce. With AIDS and other viral diseases, such a feat could cripple the disease's ability to spread.

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