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XRCC4 Protein Interactions with XRCC4‐like Factor (XLF) Create an Extended Grooved Scaffold for DNA Ligation and Double Strand Break Repair
Author(s) -
Hammel Michal,
Rey Martial,
Yu Yaping,
LeesMiller Susan,
Tainer John
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.758.8
Subject(s) - dna repair protein xrcc4 , non homologous end joining , dna ligase , dna repair , dna , biology , chemistry , genetics , dna mismatch repair
The XRCC4‐like factor (XLF)‐XRCC4 complex is essential for nonhomologous end joining, the major repair pathway for DNA double strand breaks in human cells. Yet, how XLF binds XRCC4 and impacts nonhomologous end joining functions has been enigmatic. Here, we report the XLF‐XRCC4 complex crystal structure in combination with biophysical and mutational analyses to define the XLF‐XRCC4 interactions. Crystal and solution structures plus mutations characterize alternating XRCC4 and XLF head domain interfaces forming parallel superhelical filaments. XLF Leu‐115 (“Leu‐lock”) inserts into a hydrophobic pocket formed by XRCC4 Met 59, Met‐61, Lys‐65, Lys‐99, Phe‐106, and Leu‐108 in synergy with pseudo‐symmetric beta‐zipper hydrogen bonds to drive specificity. XLF C terminus and DNA enhance parallel filament formation. Super‐helical XLF‐XRCC4 filaments form a positively charged channel to bind DNA and align ends for efficient ligation. Collective results reveal how human XLF and XRCC4 interact to bind DNA, suggest consequences of patient mutations, and support a unified molecular mechanism for XLF‐XRCC4 stimulation of DNA ligation.