Polarized Displacement by Transcription Activator-like Effectors for Regulatory Circuits

Activity of genes is defined by proteins that bind to the DNA in their close proximity. Transcription Activator-Like Effector (TALE) proteins can be designed to bind almost any selected DNA sequence. Researchers at the Department of Synthetic Biology and Immunology at NIC reported several years ago that TALEs can be used to introduce logic functions into mammalian cells. Now researchers from the same group report in an article in Nature Chemical Biology that TALE proteins can displace other TALE proteins from the DNA in a highly polarized manner –the displacement of a TALE can occur only by binding of another TALE protein to the DNA sequence adjacent to its left but not its right side. Based on a chained displacement of several adjacent TALE proteins, the researchers managed to implement all two-input logic circuits in human cells.

This unusual property of TALEs has been used to increase the precision of regulation of gene expression, for design of logic circuits in mammalian cells and to prevent CRISPR-mediated cleavage at non-desired DNA sites.

Researchers believe that the discovery is important both for understanding the mechanism of rearrangement of molecular complexes in nature, as well as for increasing the accuracy, safety and efficacy of cell therapy or for biotechnological use.

Disassembly of molecular complexes by binding of other molecules is an important principle in nature and this report is probably the first case where the displacement has been engineered on purpose and used for a completely new goal. Researchers claim that this discovery is important both for understanding the mechanism of facilitated displacement in nature and for increasing the precision, safety and efficiency of cell therapy or biotechnological production. The research was funded by the Slovenian Research Agency.

Ilustration of the principle of TALE-displacement principle can be viewed in the animation:

Reference: Tina Lebar, Anže Verbič, Ajasja Ljubetič, Roman Jerala: Polarized displacement by transcription activator-like effectors for regulatory circuits’ Nature Chemical Biology 2018, available as an Advanced Online Publication DOI: 10.1038/s41589-018-0163-8

 Application of molecular displacement based on TALE proteins for the design of gene circuits.

Dr. Tina Lebar takes her research very seriously and displays a tattoo of the TALEs, CRISPR and logic functions on her arm.