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SAP domain forms a flexible part of DNA aperture in Ku70/80
Author(s) -
Hnízda Aleš,
Tesina Petr,
Nguyen ThanhBinh,
Kukačka Zdeněk,
Kater Lukas,
Chaplin Amanda K.,
Beckmann Roland,
Ascher David B.,
Novák Petr,
Blundell Tom L.
Publication year - 2021
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.15732
Subject(s) - ku70 , dna , hmg box , biophysics , dna ligase , dna repair , dna clamp , chemistry , biology , crystallography , physics , genetics , dna binding protein , gene , polymerase chain reaction , reverse transcriptase , transcription factor
Nonhomologous end joining (NHEJ) is a DNA repair mechanism that religates double‐strand DNA breaks to maintain genomic integrity during the entire cell cycle. The Ku70/80 complex recognizes DNA breaks and serves as an essential hub for recruitment of NHEJ components. Here, we describe intramolecular interactions of the Ku70 C‐terminal domain, known as the SAP domain. Using single‐particle cryo‐electron microscopy, mass spectrometric analysis of intermolecular cross‐linking and molecular modelling simulations, we captured variable positions of the SAP domain depending on DNA binding. The first position was localized at the DNA aperture in the Ku70/80 apo form but was not observed in the DNA‐bound state. The second position, which was observed in both apo and DNA‐bound states, was found below the DNA aperture, close to the helical arm of Ku70. The localization of the SAP domain in the DNA aperture suggests a function as a flexible entry gate for broken DNA. Databases EM maps have been deposited in EMDB (EMD‐11933). Coordinates have been deposited in Protein Data Bank (PDB 7AXZ ). Other data are available from corresponding authors upon a request.