Edited by Allan H. Conney, Rutgers, The State University of New Jersey, Piscataway, NJ, and approved August 7, 2009 (received for review June 30, 2009)
Organisms require faithful DNA replication to avoid deleterious mutations. In yeast, replicative leading- and lagging-strand DNA polymerases (Pols ε and δ, respectively) have intrinsic proofreading exonucleases that cooperate with each other and mismatch repair to limit spontaneous mutation to less than 1 per genome per cell division. The relationship of these pathways in mammals and their functions in vivo are unknown. Here we show that mouse Pol ε and δ proofreading suppress discrete mutator and cancer phenotypes. We found that inactivation of Pol ε proofreading elevates base-substitution mutations and accelerates a unique spectrum of spontaneous cancers; the types of tumors are entirely different from those triggered by loss of Pol δ proofreading. Intercrosses of Pol ε-, Pol δ-, and mismatch repair-mutant mice show that Pol ε and δ proofreading act in parallel pathways to prevent spontaneous mutation and cancer. These findings distinguish Pol ε and δ functions in vivo and reveal tissue-specific requirements for DNA replication fidelity.
Author contributions,: T.M.A., M.O., J.M.B., L.E.H., Y.C., Y.W., J.A.H., R.E.G., and B.D.P. designed research; T.M.A., M.O., J.M.B., L.E.H., Y.C., Y.W., and R.E.G. performed research; R.E.G. contributed new reagents/analytic tools; T.M.A., M.O., J.M.B., L.E.H., Y.C., Y.W., P.M.T., J.A.H., R.E.G., and B.D.P. analyzed data; and T.M.A. and B.D.P. wrote the paper.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0907147106/DCSupplemental.
