Molecular Evolution of the Tre Recombinase

Published 5/29/2008
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Summary

Here we report the generation of Tre recombinase through directed, molecular evolution. Tre recombinase recognizes a pre-defined target sequence within the LTR sequences of the HIV-1 provirus, resulting in the excision and eradication of the provirus from infected human cells. While still in its infancy, directed molecular evolution will allow the creation of custom enzymes that will serve as tools of molecular surgery and molecular medicine.

Cite this Article

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Buchholz, F. Molecular Evolution of the Tre Recombinase. J. Vis. Exp. (15), e791, doi:10.3791/791 (2008).

Abstract

Here we report the generation of Tre recombinase through directed, molecular evolution. Tre recombinase recognizes a pre-defined target sequence within the LTR sequences of the HIV-1 provirus, resulting in the excision and eradication of the provirus from infected human cells.

We started with Cre, a 38-kDa recombinase, that recognizes a 34-bp double-stranded DNA sequence known as loxP. Because Cre can effectively eliminate genomic sequences, we set out to tailor a recombinase that could remove the sequence between the 5'-LTR and 3'-LTR of an integrated HIV-1 provirus. As a first step we identified sequences within the LTR sites that were similar to loxP and tested for recombination activity. Initially Cre and mutagenized Cre libraries failed to recombine the chosen loxLTR sites of the HIV-1 provirus. As the start of any directed molecular evolution process requires at least residual activity, the original asymmetric loxLTR sequences were split into subsets and tested again for recombination activity. Acting as intermediates, recombination activity was shown with the subsets. Next, recombinase libraries were enriched through reiterative evolution cycles. Subsequently, enriched libraries were shuffled and recombined. The combination of different mutations proved synergistic and recombinases were created that were able to recombine loxLTR1 and loxLTR2. This was evidence that an evolutionary strategy through intermediates can be successful. After a total of 126 evolution cycles individual recombinases were functionally and structurally analyzed. The most active recombinase -- Tre -- had 19 amino acid changes as compared to Cre. Tre recombinase was able to excise the HIV-1 provirus from the genome HIV-1 infected HeLa cells (see "HIV-1 Proviral DNA Excision Using an Evolved Recombinase", Hauber J., Heinrich-Pette-Institute for Experimental Virology and Immunology, Hamburg, Germany). While still in its infancy, directed molecular evolution will allow the creation of custom enzymes that will serve as tools of "molecular surgery" and molecular medicine.

Disclosures

The authors have nothing to disclose.

Comments

3 Comments

  1. Dr. Frank Buchholz,

    Its nice to listen to the talk. I have some queries about Tre recombinase.,
     
    1, to excise a fragment using cre or tre i guess, there should be two loxp sites if you are targeting HIV LTR region it should be very specific region rather conserved region. So what happens if the LTR regions tend to mutate ?
    ², Isn't molecular evolution a long process to create such an recombinase ?

    3, There are "zinc finger nuclease" which are custom made enzyme which make specific cuts at DNA. It has the ability to bind to any piece of DNA. So will this technique be useful  for making "Zinc Finger Recombinase", which has the ability to bind LTR region and excise the whole or part of HIV genome.

    Hoping for your comments

    Roshan Padmanabhan
    India  

    Reply
    Posted by: Anonymous
    June 26, 2008 - 12:40 PM
  2. TRE can eradiction Lentiviral Vector from transducted cell fully? if Yes you can find different beatween Tat-Dependent and Tat-Independent LV as target for eradiction 5LTR-LTR3 from genome integrated sit? Sincerely

    Reply
    Posted by: Anonymous
    September 22, 2008 - 7:24 AM
  3. Hello Dr. Frank Bucholz,
    Have you sequenced the host cell genome in the wild type control vs. the HIV-1 infected vs Tre recombinase cells to
    definitively show where the HIV-1 genome is inserting, and that it is removed? Much evidence points to nonrandom insertion
    of the HIV-1 genome.
    Doug Cork
    MHRP/HJF (dcork@hivresearch.org)

    Reply
    Posted by: Anonymous
    October 21, 2009 - 10:06 AM

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