Mechanisms of nonhomologous DNA end-joining in frogs, mice and men.
DNA end-joining, a process related to illegitimate recombination and capable of rejoining unrelated pairs of DNA ends in the absence of sequence homology, is considered the major pathway of double-strand break (DSB) repair in mammalian cells. Whole cell and nuclear extracts from three human and one mouse cell line were investigated for their capacities to promote nonhomologous DNA end-joining and their relative activities of DNA-PK, a mammalian DNA end-binding protein complex implicated in DSB-repair. The levels of DNA end-joining and the spectra of junctions of the human systems were identical with the ones of a previously described cell-free joining system derived from Xenopus laevis eggs. Due to the presence of potent 3'-5'-exonuclease activities the mouse system displayed decreased levels of DNA end-joining and larger fractions of junctions containing deletions but otherwise the basic mechanisms of junction formation appeared to be identical with the Xenopus system. DNA-PK activity was found to be equally low in the Xenopus and the mouse system but 4- to 6-fold increased in the human systems. Our results suggest that the mechanisms of DNA end-joining may be modulated by the level of exonuclease activities and/or DNA end-protecting factors but are otherwise highly conserved in vertebrate cells.
Daza
P
P
Institut für Genetik, Universität zu Köln, Germany.
Reichenberger
S
S
Göttlich
B
B
Hagmann
M
M
Feldmann
E
E
Pfeiffer
P
P
D000818:Animals; D004247:DNA / Q000378:metabolism*; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005347:Fibroblasts / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D007700:Kinetics; D008297:Male; D051379:Mice; D009687:Nuclear Proteins; D009865:Oocytes / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011995:Recombination, Genetic; D015183:Restriction Mapping; D017384:Sequence Deletion; D014982:Xenopus laevis
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases