forkhead associated (FHA) domain found in aprataxin, bifunctional polynucleotide phosphatase/kinase (PNKP), aprataxin and PNK-like factor (APLF), and similar proteins
The family includes aprataxin, PNKP, and APLF. Aprataxin (EC 3.6.1.71/EC 3.6.1.72), also called forkhead-associated domain histidine triad-like protein (FHA-HIT), is a DNA-binding protein involved in single-strand DNA break repair, double-strand DNA break repair, and base excision repair. It catalyzes the release of adenylate groups covalently linked to 5'-phosphate termini, resulting in the production of 5'-phosphate termini that can be efficiently rejoined. It can also hydrolyze adenosine 5'-monophosphoramidate (AMP-NH(2)) and diadenosine tetraphosphate (AppppA), but with lower catalytic activity. Likewise, it catalyzes the release of 3'-linked guanosine (DNAppG) and inosine (DNAppI) from DNA but has higher specific activity with 5'-linked adenosine (AppDNA). PNKP (EC 3.1.3.32/EC 2.7.1.78), also called DNA 5'-kinase/3'-phosphatase, or polynucleotide kinase-3'-phosphatase, plays a key role in the repair of DNA damage, functioning as part of both the non-homologous end-joining (NHEJ) and base excision repair (BER) pathways. Through its two catalytic activities, PNKP ensures that DNA termini are compatible with extension and ligation by either removing 3'-phosphates from, or by phosphorylating 5'-hydroxyl groups on, the ribose sugar of the DNA backbone. APLF, also called apurinic-apyrimidinic endonuclease APLF, PNK and APTX-like FHA domain-containing protein, or XRCC1-interacting protein 1 (XIP1), is a novel apurinic-apyrimidinic (AP) endonuclease and 3'-5' exonuclease with conserved zinc-finger-like motifs involved in single-strand and double-strand DNA break repair. It is recruited to sites of DNA damage through interaction with poly(ADP-ribose), a polymeric post-translational modification synthesized transiently at sites of chromosomal damage to accelerate DNA strand break repair reactions. It can introduce nicks at hydroxyuracil and other types of pyrimidine base damage. Together with PARP3, APLF promotes the retention of the LIG4-XRCC4 complex on chromatin and accelerate DNA ligation during non-homologous end-joining (NHEJ). Members of this family contain an FHA domain at their N-terminus. The FHA domain is a small phosphopeptide recognition module.
Jiyao W et al.(2023). "The conserved domain database in 2023.",