Off-target genomic DNA sites with partial homology to TALEN recognition sequences (TALEN off-target sites)

Off-target genomic DNA sites with partial homology to TALEN recognition sequences are unintended locations within the genome where Transcription Activator-Like Effector Nucleases (TALENs) bind and exert catalytic activity (Miller et al., 2011, Nature Biotechnology). TALENs are chimeric proteins composed of a customizable DNA-binding domain and a FokI nuclease domain, designed to create targeted double-strand breaks (DSBs) for gene editing. However, due to the inherent flexibility of TALE-DNA interactions, these nucleases can recognize and cleave sequences that differ by several nucleotides from the intended target (Mussolino et al., 2011, Nucleic Acids Research). Such off-target cleavage can lead to permanent mutations, including insertions and deletions (indels), or large-scale chromosomal translocations during the cellular DNA repair process (Frock et al., 2015, Nature Biotechnology). In a clinical context, these events pose severe safety risks, such as the potential for oncogenic transformation if off-target effects occur within or near critical regulatory genes or tumor suppressors. Consequently, identifying and characterizing these sites using high-throughput sequencing and bioinformatic tools is essential for the safety assessment of TALEN-based gene therapies.

Other names

TALEN off-targetsOff-target cleavage sitesNon-specific TALEN binding sitesHomologous off-target sequencesTALEN-mediated off-target mutations

Unintended DNA double-strand breaks (DSBs) induced by TALEN binding to sequences with partial homology, followed by error-prone DNA repair mechanisms like non-homologous end joining (NHEJ) (Guilinger et al., 2014, Nature Methods).