Transforming RNA into DNA: Cool OOL Research

Added Later: The entire research paper is available Conversion of a Ribozyme to a Deoxyribozyme
through In Vitro Evolution

This is interesting. According to Science Daily scientists at The Scripps Research Institute have successfully converted RNA to DNA through the use of in vitro evolution (we are not talking about translation). From the Science Daily article:

The molecular conversion or transfer of both genetic information and catalytic function between these two different genetic systems, which are both based on nucleic acid-like molecules, is exactly what many scientists believe occurred during the very earliest period of earth’s existence.
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.


Incidently, before going further, you kind find an exxplanation of in vitro evolution here.
The importance of this research lies in the transfer of catalytic function from RNA to DNA:

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.

More importantly:

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.

*snip*

There are several candidates for the initial pre-RNA molecule, all of which have the ability to form base-paired structures with themselves and with RNA. Cross-pairing would allow genetic information to be transferred from these pre-RNA molecules to RNA. The catalytic function of these early enzymes might have been transferred to a corresponding RNA enzyme following the acquisition of a few critical mutations, the study said, just as the evolutionary change of a ribozyme to a deoxyribozyme with the same or similar catalytic functions might also have occurred through random mutation and selection.

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8 Responses

  1. This is interesting stuff. One of the main knocks on the RNA World hypothesis is that this is actually (primarily) a DNA World, and how did we get from one the other?
    Interesting to see how this pans out. Thanks for the update.

  2. The interesting part, to me, is that this may be one of several pathways for this change over to occur…

  3. Have to see the full article to know what catalytic function(s) is/are being selected for. Ribozymes have diverse functions, including some of the most critical events in “real” life processes such as peptide bond formation and RNA processing. DNA, on the other hand, is rather inept catalytically, at least in vivo. Rather, it mainly serves as information source in replication and transcription (including regulation). So, just what event in the RNA world hypothesis this demonstration is supposed to mimic is not clear to me. Even after you get to DNA, RNA is still essential.

  4. As I understand it, they succeded in transfering the catalytic function of RNA to DNA.

  5. I tracked down the paper, it is freely available at the link above.

  6. Let me get this straight:They took a ribozyme, switched the U for T, and it lost activity. Then they were able to make millions of variants of that sequence, and find one that had the activity again.
    Nothing really got transferred here, did it?
    If they started with a random string of deoxynucleotides, would it have taken longer to “evolve” the activity?

  7. Unless you count the catalytic ability…which was just as efficient in the converted DNA as the original RNA:

    This DNA molecule was used as
    a starting point to generate a population of random variants,
    which were selected for the ability to catalyze the
    RNA ligation reaction. Ten rounds of in vitro evolution
    were carried out, resulting in a deoxyribozyme with RNA
    ligase activity.

    This kind of transfer of function is a necessary step in going from a RNA world to a DNA world (or from a pre-RNA world to a RNA world). That this study demostrates that such a transfer is possible is a small step in solving the OOL.

  8. What are (half) of you guys talking about? This is nothing more than demonstrating that DNA can be catalytic.
    Grady and Hartman got it right. What’s all this ‘transfer of function’ and ‘changing’ from an RNA to DNA world talk about?
    This is so less important to understanding our origins than some of you believe. Now, if a deoxyribozyme had been discovered in nature, that would be paradox shaking news!

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