Evidence for extrinsic exonucleolytic proofreading.

Abstract
Exonucleolytic proofreading of DNA synthesis errors is one of the major determinants ofgenome stability. However, many DNA transactions that contribute to genome stability requiresynthesis by polymerases that naturally lack intrinsic 3´ exonuclease activity and some of whichare highly inaccurate. Here we discuss evidence that errors made by these polymerases may beedited by a separate 3´ exonuclease, and we consider how such extrinsic proofreading may differfrom proofreading by exonucleases that are intrinsic to replicative DNA polymerases.