Three-dimensional Structure and Function of Replication Protein A
- *Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037;†Department of Biochemistry and Molecular Biology, University of Oklahoma Health Science Center, Oklahoma City, Oklahoma 73190; ‡Departments of Biochemistry and Physics, and Center for Structural Biology, Vanderbilt University, Nashville, Tennesse 37232; §Department of Medical Biophysics, Ontario Cancer Institute, Toronto, Ontario Canada M5G 2M9; #Banting and Best Department of Medical Research, C.H. Best Institute, Toronto, Ontario Canada M5G 1L6
This extract was created in the absence of an abstract.
Excerpt
Replication protein A (RPA), the most abundant single-stranded DNA (ssDNA)-binding protein in eukaryotes, participates in nearly every aspect of DNA maintenance and is necessary for cell viability. RPA wasoriginally identified as an indispensable component ofDNA replication of simian virus 40 (SV40) (Wobbe et al.1987; Fairman and Stillman 1988; Wold and Kelly 1988).Later, it was also found to be involved in DNA recombination, and in the nucleotide excision, base excision, andrecombinational pathways of DNA repair (Wold 1997;Iftode et al. 1999). Although it is clear that RPA is essential in all of these processes, its exact role is not totally understood. RPA has no enzymatic activity; it binds tightlyto ssDNA in a defined orientation and establishes proteinprotein contacts with components of the DNA replication, recombination, and repair machinery. Since ssDNAis a common intermediate in DNA replication, recombination, and repair, one possible function that can be attributed to RPA is to protect ssDNA from nucleolyticdegradation or other modifications. RPA may also have amore active role of reducing the conformational entropyof ssDNA. Applying a mechanical tension on an ssDNAtemplate significantly increases the rate of DNA polymerization by decreasing the entropy of DNA and, consequently, the energetic cost of the work done by thepolymerase (Wuite et al. 2000). The applied tension onssDNA may mimic the effect of RPA binding. The ability of RPA to simultaneously bind ssDNA and mediateinteractions with multiple proteins may be necessary forthe ordered assembly of DNA replication and repaircomplexes if for no other reason than to establish the correct orientation of the first proteins in the pathway withrespect to the 5′-3′ polarity of DNA (de Laat et al. 1998;Iftode and Borowiec 2000). In fact, recent data suggestthat RPA participates not only in the initiation, but also inthe subsequent steps of the ordered assembly of replication and repair proteins by means of a competition-basedmechanism where proteins trade places for binding to acommon site on RPA (Yuzhakov et al. 1999; Kowalczykowski 2000; Mer et al. 2000b)...
