title: Two essential but distinct functions of the mammalian abasic endonuclease.
abstract: The mammalian abasic endonuclease, APE1, has two distinct roles in the repair of oxidative DNA damage and in gene regulation. Here we show that both functions are essential for cell survival. Deletion of the APE1 gene causes embryonic lethality in mice, and no nullizygous embryo fibroblasts have been isolated. We have now established nullizygous embryo fibroblast lines from APE1(-/-) mouse embryos that are transgenic with the "floxed" human APE1 (hAPE1) gene. Removal of hAPE1 by Cre expression through nuclear microinjection elicited apoptosis in these cells within 24 h, which was blocked by coinjection of the wild-type hAPE1 gene. In contrast, mutant hAPE1 alleles, lacking either the DNA repair or acetylation-mediated gene regulatory function, could not prevent apoptosis, although the combination of these two mutants complemented APE deficiency induced by Cre. These results indicate that distinct and separable functions of APE1 are both essential for mammalian cells even in vitro and provide the evidence that mammalian cells, unlike yeast or Escherichia coli, absolutely require APE for survival, presumably to protect against spontaneous oxidative DNA damage.
authors.affiliation: Sealy Center for Molecular Science, Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Tadahide
authors.initials: T
authors.lastname: Izumi
authors.forename: David B
authors.initials: DB
authors.lastname: Brown
authors.forename: C V
authors.initials: CV
authors.lastname: Naidu
authors.forename: Kishor K
authors.initials: KK
authors.lastname: Bhakat
authors.forename: Mark A
authors.initials: MA
authors.lastname: Macinnes
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Saito
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
authors.forename: Sankar
authors.initials: S
authors.lastname: Mitra
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008845:Microinjections; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D011993:Recombinant Fusion Proteins; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase