6tyv
Structure of Ku80 von Willebrand domain complexed with WRN Ku Binding Motif
Structural highlights
DiseaseWRN_HUMAN Defects in WRN are a cause of Werner syndrome (WRN) [MIM:277700. WRN is a rare autosomal recessive progeroid syndrome characterized by the premature onset of multiple age-related disorders, including atherosclerosis, cancer, non-insulin-dependent diabetes mellitus, ocular cataracts and osteoporosis. The major cause of death, at a median age of 47, is myocardial infarction. Currently all known WS mutations produces prematurely terminated proteins.[1] Defects in WRN may be a cause of colorectal cancer (CRC) [MIM:114500. FunctionWRN_HUMAN Multifunctional enzyme that has both magnesium and ATP-dependent DNA-helicase activity and 3'->5' exonuclease activity towards double-stranded DNA with a 5'-overhang. Has no nuclease activity towards single-stranded DNA or blunt-ended double-stranded DNA. Binds preferentially to DNA substrates containing alternate secondary structures, such as replication forks and Holliday junctions. May play an important role in the dissociation of joint DNA molecules that can arise as products of homologous recombination, at stalled replication forks or during DNA repair. Alleviates stalling of DNA polymerases at the site of DNA lesions. Important for genomic integrity. Plays a role in the formation of DNA replication focal centers; stably associates with foci elements generating binding sites for RP-A (By similarity).[2] [3] [4] [5] [6] Publication Abstract from PubMedThe N-terminal von Willebrand domain of Ku80 supports interactions with a Ku binding motif (KBM) that has been identified in at least three other DNA repair proteins: the non-homologous end joining (NHEJ) scaffold APLF, the modulator of retrovirus infection, MRI, and the Werner syndrome protein (WRN). A second, more recently identified Ku binding motif present in XLF and several other proteins (KBMX) has also been reported to interact with this domain. The isolated Ku80 von Willebrand antigen domain (vWA) from Xenopus laevis has a sequence that is 60% identical with the human domain, is readily expressed and has been used to investigate these interactions. Structural characterization of the complexes formed with the KBM motifs in human APLF, MRI, and WRN identify a conserved binding site that is consistent with previously-reported mutational studies. In contrast with the KBM binding site, structural studies indicate that the KBMX site is occluded by a distorted helix. Fluorescence polarization and (19)F NMR studies of a fluorinated XLF C-terminal peptide failed to indicate any interaction with the frog vWA. It was hypothesized that availability of this binding site is conditional, i.e., dependent on specific experimental conditions or other repair factors to make the site available for binding. Modulating the fraction of KBMX-accessible binding site mutationally demonstrated that the more open site is capable of binding the KBMX(XLF) motif peptide. It is suggested that the conditional nature of KBMX binding limits formation of non-productive complexes so that activation-dependent site availability can more optimally support advancing the synapsis process. Ligand binding characteristics of the Ku80 von Willebrand domain.,Kim K, Min J, Kirby TW, Gabel SA, Pedersen LC, London RE DNA Repair (Amst). 2019 Oct 24;85:102739. doi: 10.1016/j.dnarep.2019.102739. PMID:31733588[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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