XRCC4's interaction with XLF is required for coding (but not signal) end joining.
XRCC4 and XLF are structurally related proteins important for DNA Ligase IV function. XRCC4 forms a tight complex with DNA Ligase IV while XLF interacts directly with XRCC4. Both XRCC4 and XLF form homodimers that can polymerize as heterotypic filaments independently of DNA Ligase IV. Emerging structural and in vitro biochemical data suggest that XRCC4 and XLF together generate a filamentous structure that promotes bridging between DNA molecules. Here, we show that ablating XRCC4's affinity for XLF results in DNA repair deficits including a surprising deficit in VDJ coding, but not signal end joining. These data are consistent with a model whereby XRCC4/XLF complexes hold DNA ends together--stringently required for coding end joining, but dispensable for signal end joining. Finally, DNA-PK phosphorylation of XRCC4/XLF complexes disrupt DNA bridging in vitro, suggesting a regulatory role for DNA-PK's phosphorylation of XRCC4/XLF complexes.
College of Veterinary Medicine and Departments of Microbiology & Molecular Genetics, Michigan State University, East Lansing, Michigan 48824, USA.
Sunetra
S
Roy
Sara N
SN
Andres
Alexandra
A
Vergnes
Jessica A
JA
Neal
Yao
Y
Xu
Yaping
Y
Yu
Susan P
SP
Lees-Miller
Murray
M
Junop
Mauro
M
Modesti
Katheryn
K
Meek
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D002470:Cell Survival; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D059766:DNA End-Joining Repair; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000378:metabolism*; D051747:DNA-Activated Protein Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D009154:Mutation; D010766:Phosphorylation; D011836:Radiation Tolerance; D060152:V(D)J Recombination
D004268:DNA-Binding Proteins; C000607893:LIG4 protein, human; C508551:NHEJ1 protein, human; C101467:XRCC4 protein, human; D004247:DNA; D051747:DNA-Activated Protein Kinase; D011088:DNA Ligases; D045643:DNA Repair Enzymes; D000072481:DNA Ligase ATP