The role of DNA dependent protein kinase in synapsis of DNA ends

DNA dependent protein kinase (DNA‐PK) plays a central role in the non‐homologous end‐joining pathway of DNA double strand break repair. Its catalytic subunit (DNA‐PKCS) functions as a serine/threonine protein kinase. We show that DNA‐PK forms a stable complex at DNA termini that blocks the action of...

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Bibliographic Details
Published in:Nucleic acids research 2003-12, Vol.31 (24), p.7238-7246
Main Authors: Weterings, Eric, Verkaik, Nicole S., Brüggenwirth, Hennie T., Hoeijmakers, Jan H. J., van Gent, Dik C.
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Catalysis
DNA - chemistry
DNA - metabolism
DNA Footprinting
DNA Ligases - metabolism
DNA-Activated Protein Kinase
DNA-Binding Proteins - metabolism
double-strand break repair
Escherichia coli - enzymology
Humans
Models, Biological
non-homologous end joining
Nuclear Proteins
Phosphorylation
Protein Binding
Protein-Serine-Threonine Kinases - metabolism
Recombination, Genetic
synapsis
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Summary:DNA dependent protein kinase (DNA‐PK) plays a central role in the non‐homologous end‐joining pathway of DNA double strand break repair. Its catalytic subunit (DNA‐PKCS) functions as a serine/threonine protein kinase. We show that DNA‐PK forms a stable complex at DNA termini that blocks the action of exonucleases and ligases. The DNA termini become accessible after autophosphorylation of DNA‐PKCS, which we demonstrate to require synapsis of DNA ends. Interestingly, the presence of DNA‐PK prevents ligation of the two synapsed termini, but allows ligation to another DNA molecule. This alteration of the ligation route is independent of the type of ligase that we used, indicating that the intrinsic architecture of the DNA‐PK complex itself is not able to support ligation of the synapsed DNA termini. We present a working model in which DNA‐PK creates a stable molecular bridge between two DNA ends that is remodeled after DNA‐PK autophosphorylation in such a way that the extreme termini become accessible without disrupting synapsis. We infer that joining of synapsed DNA termini would require an additional protein factor.
ISSN:0305-1048
1362-4962
1362-4962
DOI:10.1093/nar/gkg889