Published online 1 December 2004
Nucleic Acids Research, Vol. 32 No. 21 © Oxford University Press 2004; all rights reserved
DNA polymerase 
, RFC and PCNA are required for repair synthesis of large looped heteroduplexes in Saccharomyces cerevisiae
The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA and 1 Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St Louis, MO 63310, USA
* To whom correspondence should be addressed. Tel: +1 402 559 4619; Fax: +1 402 559 8290; Email: rlahue{at}unmc.edu
Received October 12, 2004; Revised and Accepted November 9, 2004
Small looped mispairs are corrected by DNA mismatch repair (MMR). In addition, a distinct process called large loop repair (LLR) corrects loops up to several hundred nucleotides in extracts of bacteria, yeast or human cells. Although LLR activity can be readily demonstrated, there has been little progress in identifying its protein components. This study identified some of the yeast proteins responsible for DNA repair synthesis during LLR. Polyclonal antisera to either Pol31 or Pol32 subunits of polymerase 
efficiently inhibited LLR in extracts by blocking repair just prior to gap filling. Gap filling was inhibited regardless of whether the loop was retained or removed. These experiments suggest polymerase is uniquely required in yeast extracts for LLR-associated synthesis. Similar results were obtained with antisera to the clamp loader proteins Rfc3 and Rfc4, and to PCNA, i.e. LLR was inhibited just prior to gap filling for both loop removal and loop retention. Thus PCNA and RFC seem to act in LLR only during repair synthesis, in contrast to their roles at both pre- and post-excision steps of MMR. These biochemical experiments support the idea that yeast polymerase , RFC and PCNA are required for large loop DNA repair synthesis.
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