This "evolutionary conversion" provides a modern-day snapshot of how life as we understand it may have first evolved out of the earliest primordial mix of RNA-like molecules-sometimes referred to as the "pre-RNA world"-into a more complex form of RNA-based life (or the "RNA world") and eventually to cellular life based on DNA and proteins. Nucleic acids are large complex molecules that store and convey genetic information, but can also function as enzymes.

While the transfer of sequence information between two different classes of nucleic acid-like molecules-between RNA and DNA, for example-is straightforward because it relies on the one-to-one correspondence of the double helix pairing, transferring catalytic function is significantly more difficult because function cannot be conveyed sequentially. The present study demonstrates that the "evolutionary conversion" of an RNA enzyme to a DNA enzyme with the same function is possible, however, through the acquisition of a few critical mutations.

The study was released in an advance online version of the journal Chemistry & Biology.

Scripps Research Professor Gerald F. Joyce, a member of the Skaggs Institute for Chemical Biology whose laboratory conducted the study, said, "During early life on earth both genetic information and catalytic function were thought to reside only in RNA. In our study, the evolutionary transition from an RNA to a DNA enzyme represents a genuine change, rather than a simple expansion, of the chemical basis for catalytic function. This means that similar evolutionary pathways may exist between other classes of nucleic acid-like molecules. These findings could help answer some fundamental questions concerning the basic structure of life and how it evolved over time."

As Francis Crick, the Nobel laureate who, along with James Watson uncovered the double helix structure of DNA, articulated in 1970, all known organisms operate according to the central dogma of mo
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Contact: Keith McKeown
kmckeown@scripps.edu
858-784-8134
Scripps Research Institute
27-Mar-2006

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