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Published June 18, 1999 | public
Journal Article Open

Human Exonuclease 1 Functionally Complements Its Yeast Homologues in DNA Recombination, RNA Primer Removal, and Mutation Avoidance

Abstract

Yeast exonuclease 1 (Exo1) is induced during meiosis and plays an important role in DNA homologous recombination and mismatch correction pathways. The human homolog, an 803-amino acid protein, shares 55% similarity to the yeast Exo1. In this report, we show that the enzyme functionally complements Saccharomyces cerevisiae Exo1 in recombination of direct repeat DNA fragments, UV resistance, and mutation avoidance by in vivo assays. Furthermore, the human enzyme suppresses the conditional lethality of a rad27Delta mutant, symptomatic of defective RNA primer removal. The purified recombinant enzyme not only displays 5'-3' double strand DNA exonuclease activity, but also shows an RNase H activity. This result indicates a back-up function of exonuclease 1 to flap endonuclease-1 in RNA primer removal during lagging strand DNA synthesis.

Additional Information

Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc. (Received for publication, December 1, 1998, and in revised form, March 29, 1999) We thank Dr. Adam Bailis for stimulating discussions and suggesting the use of the CYH2 assay system and Tim O'Connor, Sharon Lin, and Geoffrey Frank for critical reading of the manuscript and technical assistance. This work was supported by a National Institutes of Health, NCI Grant CA82468 (to B. H. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

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