Nick-dependent and -independent Processing of Large DNA Loops in Human Cells

Scott D. McCulloch, Liya Gu, Guo Min Li

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)50803-50809
Number of pages7
JournalJournal of Biological Chemistry
Issue number50
StatePublished - Dec 12 2003

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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