TALENs have recently swooped down and snatched the genome editing monopoly from ZFNs. TALENs operate on almost the same principle as ZFNs. TALENs are fusions of transcription activator-like (TAL) proteins and a FokI nuclease. TAL proteins are composed of 33-34 amino acid repeating motifs with two variable positions that have a strong recognition for specific nucleotides (Deng et al., 2014).
By assembling arrays of these TALs and fusing them to a FokI nuclease, specific cutting of the genome can be achieved. When two TALENs bind and meet, the FokI domains induce a double-strand break which can inactivate a gene, or can be used to insert DNA of interest (Cermak et al., 2011). TALENs are more specific than ZFNs, the monomers don’t have the cross-reactivity problem that plagued ZFN researchers. This simplicity has facilitated automation of TALEN construction (Reyon et al., 2012). On the downside, since a TAL is needed for each nucleotide, TALENs are larger and somewhat harder to deliver than ZFNs.
TALEN Additional Reading
This review examines the mechanism of TALEN system function. The authors also provide a list of papers that have used TALENs in various organisms, describe the biochemical function of the system, and discuss challenges and future perspectives.
This review compares the TALEN and CRIPSR systems. The functional differences and relative strengths a weakness of each method are discussed.
- Cermak, T., Doyle, E.L., Christian, M., Wang, L., Zhang, Y., Schmidt, C., Baller, J.A., Somia, N.V., Bogdanove, A.J., and Voytas, D.F. (2011). Efficient design and assembly of custom TALEN and other TAL effector-based constructs for DNA targeting. Nucleic Acids Res. 39, e82.
- Deng, D., Yan, C., Wu, J., Pan, X., and Yan, N. (2014). Revisiting the TALE repeat. Protein Cell.
- Reyon, D., Tsai, S.Q., Khayter, C., Foden, J.A., Sander, J.D., and Joung, J.K. (2012). FLASH assembly of TALENs for high-throughput genome editing. Nat. Biotechnol. 30, 460-+.