Hybrid Protein Developed as Tools for Gene Cutting, Editing

A U.S. team of researchers has developed a kind of hybrid proteins that can make double-strand DNA breaks at specific sites in living cells, potentially leading to better gene replacement and gene editing therapies.

Dr. Bing Yang, assistant professor of genetics, development and cell biology at Iowa State University (ISU; Ames, USA;), and his colleagues developed the hybrid protein by joining parts of two different bacterial proteins. One is called a TAL (transcription activator-like) effector, which functions to find the specific site on the gene that needs to be cut, and the other is an enzyme called a nuclease that cuts the DNA strands. Dr. Yang hopes this study will lead to the ability to engineer genomes by cutting out defective or undesirable parts of DNA, or by replacing defective or undesirable gene segments with a functioning piece of replacement DNA--a process called homologous recombination.

Dr. Yang reported that these hybrid proteins could be constructed to locate specific segments of the DNA in any sort of organism. "This breakthrough could eventually make it possible to efficiently modify plant, animal and even human genomes,” said Dr. Yang. "It should be effective in a range of organisms.”

The proteins function by binding onto the specific segment of DNA the researcher needs to change. These proteins do this by reading the DNA sequence and finding the specific area to be cut. Once the protein binds onto the DNA at the correct spot, the other half of the protein then cuts the double-stranded DNA. Bad or undesirable DNA can be resected and good or more desirable DNA can be introduced. When the DNA heals, the good DNA is included in the gene.

Dr. Yang began his project approximately one year ago after seeing the results of research by Dr. Adam Bogdanove, ISU associate professor of plant pathology, showing that TAL effectors use a very clear-cut code to bind to a specific DNA sequence. This discovery allowed Dr. Yang to predict precisely where the TAL effector nuclease will bind on the DNA to make the cut. Another study had similar results.

The conecept has also been validated by Dr. Bogdanove and Dr. Dan Voytas, collaborator in genetics, development, and cell biology at Iowa State, and director of the Center for Genome Engineering at the University of Minnesota (Twin Cities, USA). The TAL effector-nuclease approach improves on tools currently available for genome modification. It should be faster and less expensive to make TAL effector nucleases, and simpler to design them to recognize specific DNA sequences, according to Dr. Yang.

Yang's findings appeared in August 2010 in the online version of the journal Nucleic Acids Research. Dr. Voytas' and Bogdanove's study also appeared in August 2010 the journal Genetics. Dr. Voytas and Dr. Bogdanove were also able to demonstrate that the TAL effector part of the hybrid protein can be modified to target new DNA sequences.

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