title: Embryonic stem cells lacking the epigenetic regulator Cfp1 are hypersensitive to DNA-damaging agents and exhibit decreased Ape1/Ref-1 protein expression and endonuclease activity.
abstract: Modulation of chromatin structure plays an important role in the recruitment and function of DNA repair proteins. CXXC finger protein 1 (Cfp1), encoded by the CXXC1 gene, is essential for mammalian development and is an important regulator of chromatin structure. Murine embryonic stem (ES) cells lacking Cfp1 (CXXC1(-/-)) are viable but demonstrate a dramatic decrease in cytosine methylation, altered histone methylation, and an inability to differentiate. We find that ES cells lacking Cfp1 are hypersensitive to a variety of DNA-damaging agents. In addition, CXXC1(-/-) ES cells accumulate more DNA damage and exhibit decreased protein expression and endonuclease activity of AP endonuclease (Ape1/Ref-1), an enzyme involved in DNA base excision repair. Expression in CXXC1(-/-) ES cells of either the amino half of Cfp1 (amino acids 1-367) or the carboxyl half of Cfp1 (amino acids 361-656) restores normal Ape1/Ref-1 protein expression and rescues the hypersensitivity to DNA-damaging agents, demonstrating that Cfp1 contains redundant functional domains. Furthermore, retention of either the DNA-binding activity of Cfp1 or interaction with the Setd1A and Setd1B histone H3-Lys4 methyltransferase complexes is required to restore normal sensitivity of CXXC1(-/-) ES cells to DNA-damaging agents. These results implicate Cfp1 as a regulator of DNA repair processes.
authors.affiliation: Herman B Wells Center for Pediatric Research, Section of Pediatric Hematology/Oncology, Department of Pediatrics, Indiana University School of Medicine, 1044W. Walnut St. R4-W312, Indianapolis, IN 46202, USA.
authors.forename: Courtney M
authors.initials: CM
authors.lastname: Tate
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Fishel
authors.forename: Julianne L
authors.initials: JL
authors.lastname: Holleran
authors.forename: Merrill J
authors.initials: MJ
authors.lastname: Egorin
authors.forename: David G
authors.initials: DG
authors.lastname: Skalnik
mesh_terms: D000818:Animals; D002460:Cell Line; D002945:Cisplatin / Q000494:pharmacology; D004249:DNA Damage; D019175:DNA Methylation; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism*; D003850:Deoxyribonuclease I / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding / Q000187:drug effects; D015534:Trans-Activators / Q000172:deficiency / Q000378:metabolism*
chemical_list: C501971:Cxxc1 protein, mouse; D015534:Trans-Activators; D003850:Deoxyribonuclease I; C486216:Apex1 protein, mouse; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D002945:Cisplatin