Nick-dependent and -independent processing of large DNA loops in human cells.
DNA loop heterologies are products of normal DNA metabolism and can lead to severe genomic instability if unrepaired. To understand how human cells process DNA loop structures, a set of circular heteroduplexes containing a 30-nucleotide loop were constructed and tested for repair in vitro by human cell nuclear extracts. We demonstrate here that, in addition to the previously identified 5' nick-directed loop repair pathway (Littman, S. J., Fang, W. H., and Modrich, P. (1999) J. Biol. Chem. 274, 7474-7481), human cells can process large DNA loop heterologies in a loop-directed manner. The loop-directed repair specifically removes the loop structure and occurs only in the looped strand, and appears to require limited DNA synthesis. Like the nick-directed loop repair, the loop-directed repair is independent of many known DNA repair pathways, including DNA mismatch repair and nucleotide excision repair. In addition, our data also suggest that an aphidicolin-sensitive DNA polymerase is involved in the excision step of the nick-directed loop repair pathway.
McCulloch
Scott D
SD
Graduate Center for Toxicology, Lucille P. Markey Cancer Center, University of Kentucky Medical Center, Lexington, Kentucky 40536, USA.
Gu
Liya
L
Li
Guo-Min
GM
D016590:Aphidicolin / Q000494:pharmacology; D001435:Bacteriophages / Q000378:metabolism; D020137:Base Pair Mismatch; D020029:Base Pairing; D001483:Base Sequence; D015139:Blotting, Southern; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000737:chemistry*; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009692:Nucleic Acid Heteroduplexes
D004791:Enzyme Inhibitors; D009692:Nucleic Acid Heteroduplexes; D016590:Aphidicolin; D004247:DNA; D004259:DNA-Directed DNA Polymerase