Genomic thymine-adenine dinucleotide (TA dinucleotide)

Genomic thymine-adenine (TA) dinucleotides, also known as 5'-TpA-3' steps, are specific two-base sequences within the host's deoxyribonucleic acid that serve as critical structural and functional targets for various therapeutic agents. These sites are characterized by unique physical properties, including a narrow minor groove and high conformational flexibility, which facilitate the binding of specific small molecules and proteins (PubMed: 11125103). In clinical medicine, TA dinucleotides are the primary chemical targets for psoralen derivatives, such as methoxsalen, which intercalate at these sites and form covalent cross-links upon activation by ultraviolet A (UVA) light; this process is used in photochemotherapy (PUVA) to treat proliferative skin disorders like psoriasis and cutaneous T-cell lymphoma (PubMed: 10460217). Furthermore, TA dinucleotides are the obligatory integration sites for the Sleeping Beauty transposon system, a prominent tool in gene therapy used to deliver therapeutic genetic material into the host genome for treating various genetic diseases and engineering CAR-T cells (PubMed: 9353300). Despite their therapeutic utility, targeting genomic TA sites poses significant safety challenges, including the risk of secondary malignancies due to non-specific DNA damage and the potential for insertional mutagenesis if integration occurs near oncogenes (PubMed: 12110615).

Other names

5'-TpA-3' siteTA stepThymine-adenine stepTA dinucleotide step

Drugs targeting TA dinucleotides typically act through intercalation followed by photo-induced covalent cross-linking of DNA strands, or through non-covalent binding within the minor groove. In gene therapy, these sites serve as specific recognition sequences for transposase-mediated integration of therapeutic DNA sequences.