title: Variations in Prkdc and susceptibility to benzene-induced toxicity in mice.
abstract: Benzene, a carcinogen that induces chromosomal breaks, is strongly associated with leukemias in humans. Possible genetic determinants of benzene susceptibility include proteins involved in repair of benzene-induced DNA damage. The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), encoded by Prkdc, is one such protein. DNA-PKcs is involved in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break (DSB) repair. Here we compared the toxic effects of benzene on mice (C57BL/6 and 129/Sv) homozygous for the wild-type Prkdc allele and mice (129/SvJ) homozygous for a Prkdc functional polymorphism that leads to diminished DNA-PK activity and enhanced apoptosis in response to radiation-induced damage. Male and female mice were exposed to 0, 10, 50, or 100 ppm benzene for 6 h/d, 5 d/week for 2 weeks. Male mice were more susceptible to benzene toxicity compared with females. Hematotoxicity was evident in all male mice but was not seen in female mice. We observed similar, large increases in both micronucleated erythrocyte populations in all male mice. Female mice had smaller but significant increases in micronucleated cells. The p53-dependent response was induced in all strains and genders of mice following benzene exposure, as indicated by an increase in p21 mRNA levels in bone marrow that frequently corresponded with cell cycle arrest in G2/M. Prkdc does not appear to be a significant genetic susceptibility factor for acute benzene toxicity. Moreover, the role of NHEJ, mediated by DNA-PK, in restoring genomic integrity following benzene-induced DSB remains equivocal.
authors.affiliation: CIIT Centers for Health Research, Research Triangle Park, North Carolina 27709, USA. Brenda.Faiola@gsk.com
authors.forename: Brenda
authors.initials: B
authors.lastname: Faiola
authors.forename: Alison K
authors.initials: AK
authors.lastname: Bauer
authors.forename: Elizabeth S
authors.initials: ES
authors.lastname: Fuller
authors.forename: Victoria A
authors.initials: VA
authors.lastname: Wong
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Pluta
authors.forename: Diane J
authors.initials: DJ
authors.lastname: Abernethy
authors.forename: James B
authors.initials: JB
authors.lastname: Mangum
authors.forename: Jeffrey I
authors.initials: JI
authors.lastname: Everitt
authors.forename: Leslie
authors.initials: L
authors.lastname: Recio
mesh_terms: D000280:Administration, Inhalation; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001554:Benzene / Q000008:administration & dosage / Q000633:toxicity*; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis / Q000235:genetics; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects / Q000473:pathology; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006720:Homozygote; D051379:Mice; D008810:Mice, Inbred C57BL; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D009153:Mutagens / Q000008:administration & dosage / Q000633:toxicity*; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013045:Species Specificity
chemical_list: C493957:Cdkn1a protein, mouse; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D009153:Mutagens; D009687:Nuclear Proteins; D012333:RNA, Messenger; D019392:Cytochrome P-450 CYP2E1; D051747:DNA-Activated Protein Kinase; C497264:Prkdc protein, mouse; D017346:Protein Serine-Threonine Kinases; D001554:Benzene