5w7x
From Proteopedia
Crystal Structure of FHA domain of human APLF in complex with XRCC1 bisphospho peptide
Structural highlights
Function[APLF_HUMAN] Nuclease involved in single-strand and double-strand DNA break repair. 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. Displays apurinic-apyrimidinic (AP) endonuclease and 3'-5' exonuclease activities in vitro. Also able to introduce nicks at hydroxyuracil and other types of pyrimidine base damage.[1] [2] [XRCC1_HUMAN] Corrects defective DNA strand-break repair and sister chromatid exchange following treatment with ionizing radiation and alkylating agents. Publication Abstract from PubMedAprataxin and PNKP-like factor (APLF) is a DNA repair factor containing a forkhead-associated (FHA) domain that supports binding to the phosphorylated FHA domain binding motifs (FBMs) in XRCC1 and XRCC4. We have characterized the interaction of the APLF FHA domain with phosphorylated XRCC1 peptides using crystallographic, NMR, and fluorescence polarization studies. The FHA-FBM interactions exhibit significant pH dependence in the physiological range as a consequence of the atypically high pK values of the phosphoserine and phosphothreonine residues and the preference for a dianionic charge state of FHA-bound pThr. These high pK values are characteristic of the polyanionic peptides typically produced by CK2 phosphorylation. Binding affinity is greatly enhanced by residues flanking the crystallographically-defined recognition motif, apparently as a consequence of non-specific electrostatic interactions, supporting the role of XRCC1 in nuclear cotransport of APLF. The FHA domain-dependent interaction of XRCC1 with APLF joins repair scaffolds that support single-strand break repair and non-homologous end joining (NHEJ). It is suggested that for double-strand DNA breaks that have initially formed a complex with PARP1 and its binding partner XRCC1, this interaction acts as a backup attempt to intercept the more error-prone alternative NHEJ repair pathway by recruiting Ku and associated NHEJ factors. Characterization of the APLF FHA-XRCC1 phosphopeptide interaction and its structural and functional implications.,Kim K, Pedersen LC, Kirby TW, DeRose EF, London RE Nucleic Acids Res. 2017 Dec 1;45(21):12374-12387. doi: 10.1093/nar/gkx941. PMID:29059378[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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