Xeroderma pigmentosum complementation group A protein (XPA) modulates RPA-DNA interactions via enhanced complex stability and inhibition of strand separation activity

Steve M. Patrick, John J. Turchi

Research output: Contribution to journalArticle

64 Scopus citations

Abstract

Replication protein A (RPA) participates in many cellular functions including DNA replication and nucleotide excision repair. A direct interaction between RPA and the xeroderma pigmentosum group A protein (XPA) facilitates the assembly of a preincision complex during the processing of DNA damage by the nucleotide excision repair pathway. We demonstrate here the formation of a ternary RPA, XPA, and duplex cisplatin-damaged DNA complex as is evident by electrophoretic supershift analysis. The RPA-XPA complex displays modest specificity for damaged versus undamaged duplex DNA, and the RPA-XPA complex displays a greater affinity for binding duplex cisplatin-damaged DNA when compared with the RPA or XPA proteins alone, consistent with previous results. Using DNA denaturation assays, we demonstrate that the role of XPA is in the stabilization of the duplex DNA structure via inhibition of the strand separation activity of RPA. Rapid kinetic analysis indicates that the bimolecular kon of the RPA-XPA complex is 2.5-fold faster than RPA alone for binding a duplex cisplatin-damaged DNA. The dissociation rate, koff, of the RPA-XPA complex is slower than that of the RPA protein alone, suggesting that the XPA protein stabilizes the initial binding of RPA to duplex DNA as well as maintaining the integrity of the duplex DNA. Interestingly, XPA has no effect on the kon of RPA for a single-stranded 40-mer DNA.

Original languageEnglish (US)
Pages (from-to)16096-16101
Number of pages6
JournalJournal of Biological Chemistry
Volume277
Issue number18
DOIs
StatePublished - May 3 2002
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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