An alternative form of replication protein A expressed in normal human tissues supports DNA repair

Michael G. Kemp, Aaron C. Mason, Aura Carreira, Joyce T. Reardon, Stuart J. Haring, Gloria E O Borgstahl, Stephen C. Kowalczykowski, Aziz Sancar, Marc S. Wold

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Replication protein A (RPA) is a heterotrimeric protein complex required for a large number of DNA metabolic processes, including DNA replication and repair. An alternative form of RPA (aRPA) has been described in which the RPA2 subunit (the 32-kDa subunit of RPA and product of the RPA2 gene) of canonical RPA is replaced by a homologous subunit, RPA4. The normal function of aRPA is not known; however, previous studies have shown that it does not support DNA replication in vitro or S-phase progression in vivo. In this work, we show that the RPA4 gene is expressed in normal human tissues and that its expression is decreased in cancerous tissues. To determine whether aRPA plays a role in cellular physiology, we investigated its role in DNA repair. aRPA interacted with both Rad52 and Rad51 and stimulated Rad51 strand exchange. We also showed that, by using a reconstituted reaction, aRPA can support the dual incision/ excision reaction of nucleotide excision repair. aRPA is less efficient in nucleotide excision repair than canonical RPA, showing reduced interactions with the repair factor XPA and no stimulation of XPF-ERCC1 endonuclease activity. In contrast, aRPA exhibits higher affinity for damaged DNA than canonical RPA, which may explain its ability to substitute for RPA in the excision step of nucleotide excision repair. Our findings provide the first direct evidence for the function of aRPA in human DNA metabolism and support a model for aRPA functioning in chromosome maintenance functions in nonproliferating cells.

Original languageEnglish (US)
Pages (from-to)4788-4797
Number of pages10
JournalJournal of Biological Chemistry
Issue number7
StatePublished - Feb 12 2010

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology


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