TALEs (Transcription Activator-Like Effectors) are proteins that
bind to DNA in a sequence-specific way. The newly-developed
transcription activator-like effectors nucleases (TALENs) comprise of a
nonspecific DNA-cleaving nuclease fused to a DNA-binding domain that can
be easily engineered so that TALENs can target essentially any
sequence. To date, the TALENs technology has become a powerful approach
for genome editing in a number of animal models.
Targeted genome editing is a common approach for efficiently modifying essentially any sequence of interest in living cells or organisms. This technology relies on the use of engineered nucleases, which are artificial proteins composed of a customizable sequence-specific DNA-binding domain fused to a nuclease that cleaves DNA in a non-sequence-specific manner. These targetable nucleases are used to induce double-strand breaks (DSBs) into specific DNA sites, which are then repaired by mechanisms that can be exploited to create sequence alterations at the cleavage site. Nuclease-mediated genome editing enables genetic studies that were previously difficult or impossible to perform.
Before the development of TALENs technology, majority of targeted genome editing has been performed using zinc finger nucleases (ZFNs), which in the past were commonly used to modify endogenous genes in a wide range of organisms and cell types. Several types of genomic alterations can be introduced with ZFNs including point mutations, deletions, insertions, inversions, duplications, and translocations. Furthermore, ZFNs can potentially be used for therapeutic purposes.
However, TALENs have rapidly developed their years as an alternative to ZFNs for genome editing and introducing targeted DSBs. TALENs are similar to ZFNs and comprise a non-specific FokI nuclease domain fused to a customizable DNA-binding domain. This DNA-binding domain is composed of highly conserved repeats derived from transcription activator-like effectors (TALEs), which are proteins secreted by Xanthomonas bacteria to alter transcription of genes in host plant cells. The fundamental building block used to engineer the DNA-binding domain of TALENs is a highly conserved repeat derived from naturally occurring TALEs encoded by Xanthomonas proteobacteria. These TALEs are injected into host plant cells via a Type III secretion system and bind to genomic DNA to alter transcription in these cells, thereby facilitating pathogenic bacteria colonization. DNA binding by these TALEs is mediated by arrays of highly conserved amino acid repeats flanked by additional TALE-derived domains at the amino- and carboxy-terminal ends of the array.
The development of TALENs has generated much interest and excitement in the world for its ease in use and convenience in labs. Over the last years, TALENs has been used to modify endogenous genes in yeast, fruit fly, roundworm, crickets, zebra fish, frog, rat, pig, cow, thale cress, rice, silkworm, pluripotent stem cells and others. The relative simplicity of using TALENs to engineer targeted gene will surely attract more attention to explore the research and therapeutic applications of customized nuclease technology.
Engineered nucleases have made it possible to achieve targeted alteration of any DNA sequence in a wide range of cell types and organisms. Gene-editing nucleases enable direct assessment of the impacts of gene disruption and of specific sequence variants on gene function in somatic cell-based models of disease. The capability of quickly and efficiently altering any gene sequence with TALENs will certainly have profound impacts on biological research and discovering potential therapies for genetic diseases.
Targeted genome editing is a common approach for efficiently modifying essentially any sequence of interest in living cells or organisms. This technology relies on the use of engineered nucleases, which are artificial proteins composed of a customizable sequence-specific DNA-binding domain fused to a nuclease that cleaves DNA in a non-sequence-specific manner. These targetable nucleases are used to induce double-strand breaks (DSBs) into specific DNA sites, which are then repaired by mechanisms that can be exploited to create sequence alterations at the cleavage site. Nuclease-mediated genome editing enables genetic studies that were previously difficult or impossible to perform.
Before the development of TALENs technology, majority of targeted genome editing has been performed using zinc finger nucleases (ZFNs), which in the past were commonly used to modify endogenous genes in a wide range of organisms and cell types. Several types of genomic alterations can be introduced with ZFNs including point mutations, deletions, insertions, inversions, duplications, and translocations. Furthermore, ZFNs can potentially be used for therapeutic purposes.
However, TALENs have rapidly developed their years as an alternative to ZFNs for genome editing and introducing targeted DSBs. TALENs are similar to ZFNs and comprise a non-specific FokI nuclease domain fused to a customizable DNA-binding domain. This DNA-binding domain is composed of highly conserved repeats derived from transcription activator-like effectors (TALEs), which are proteins secreted by Xanthomonas bacteria to alter transcription of genes in host plant cells. The fundamental building block used to engineer the DNA-binding domain of TALENs is a highly conserved repeat derived from naturally occurring TALEs encoded by Xanthomonas proteobacteria. These TALEs are injected into host plant cells via a Type III secretion system and bind to genomic DNA to alter transcription in these cells, thereby facilitating pathogenic bacteria colonization. DNA binding by these TALEs is mediated by arrays of highly conserved amino acid repeats flanked by additional TALE-derived domains at the amino- and carboxy-terminal ends of the array.
The development of TALENs has generated much interest and excitement in the world for its ease in use and convenience in labs. Over the last years, TALENs has been used to modify endogenous genes in yeast, fruit fly, roundworm, crickets, zebra fish, frog, rat, pig, cow, thale cress, rice, silkworm, pluripotent stem cells and others. The relative simplicity of using TALENs to engineer targeted gene will surely attract more attention to explore the research and therapeutic applications of customized nuclease technology.
Engineered nucleases have made it possible to achieve targeted alteration of any DNA sequence in a wide range of cell types and organisms. Gene-editing nucleases enable direct assessment of the impacts of gene disruption and of specific sequence variants on gene function in somatic cell-based models of disease. The capability of quickly and efficiently altering any gene sequence with TALENs will certainly have profound impacts on biological research and discovering potential therapies for genetic diseases.
