%0 Journal Article
%T The Polymerase Activity of Mammalian DNA Pol ¦Æ Is Specifically Required for Cell and Embryonic Viability
%A Sabine S. Lange&nbsp
%A Junya Tomida&nbsp
%A Karen S. Boulware&nbsp
%A Sarita Bhetawal&nbsp
%A Richard D. Wood
%J PLOS Genetics
%D 2016
%I Public Library of Science (PLoS)
%R 10.1371/journal.pgen.1005759
%X DNA polymerase ¦Æ (pol ¦Æ) is exceptionally important for maintaining genome stability. Inactivation of the Rev3l gene encoding the polymerase catalytic subunit causes a high frequency of chromosomal breaks, followed by lethality in mouse embryos and in primary cells. Yet it is not known whether the DNA polymerase activity of pol ¦Æ is specifically essential, as the large REV3L protein also serves as a multiprotein scaffold for translesion DNA synthesis via multiple conserved structural domains. We report that Rev3l cDNA rescues the genomic instability and DNA damage sensitivity of Rev3l-null immortalized mouse fibroblast cell lines. A cDNA harboring mutations of conserved catalytic aspartate residues in the polymerase domain of REV3L could not rescue these phenotypes. To investigate the role of REV3L DNA polymerase activity in vivo, a Rev3l knock-in mouse was constructed with this polymerase-inactivating alteration. No homozygous mutant mice were produced, with lethality occurring during embryogenesis. Primary fibroblasts from mutant embryos showed growth defects, elevated DNA double-strand breaks and cisplatin sensitivity similar to Rev3l-null fibroblasts. We tested whether the severe Rev3l-/- phenotypes could be rescued by deletion of DNA polymerase ¦Ç, as has been reported with chicken DT40 cells. However, Rev3l-/- Polh-/- mice were inviable, and derived primary fibroblasts were as sensitive to DNA damage as Rev3l-/- Polh+/+ fibroblasts. Therefore, the functions of REV3L in maintaining cell viability, embryonic viability and genomic stability are directly dependent on its polymerase activity, and cannot be ameliorated by an additional deletion of pol ¦Ç. These results validate and encourage the approach of targeting the DNA polymerase activity of pol ¦Æ to sensitize tumors to DNA damaging agents.
%U http://www.plosgenetics.org/article/info%3Adoi%2F10.1371%2Fjournal.pgen.1005759