title: Constitutive over-production of DNA-damage recognition proteins and acquired UV resistance in prolonged culture of F9 teratocarcinoma stem cells.
abstract: An ultraviolet (UV)-resistant F9 variant cell line, termed F9Vc, was established from a prolonged culture of murine F9 embryonic stem cells. A 6-fold UV resistance was detected in F9V2 cells compared to the F9 parental cells, as determined by ID50 (36 J/m2 vs. 6 J/m2), the UV dose causing 50% growth inhibition. Using a DNA mobility-shift assay, a nuclear protein (termed UVDRP) that preferentially binds to UV-damaged DNA was detected in F9 and F9Vc cell extracts. The UVDRP in F9Vc cells was present at a 7-fold higher concentration than that of F9 cells. Interestingly, the F9 UVDRP was transiently induced following cellular differentiation by retinoic acid (RA)/cAMP, with optimum induction (15-fold) at 6 days. Although constitutively over-produced, UVDRP also remained inducible in F9Vc cells in response to RA/cAMP. Indirect DNA repair measurement by host cell reactivation of UV-damaged plasmid DNA demonstrated that F9Vc cells exhibited a slight increase or a similarity in repair ability compared to the F9 cells. Parallel experiments using the repair-defective xeroderma pigmentosum (XP) group A fibroblasts and the normal VA13 fibroblasts also indicated that over-production of UVDRP binding activity was associated with enhanced DNA repair and UV resistance. The findings indicate that prolonged culture of F9 cells can establish a condition sufficient to cause constitutive over-production of UVDRP binding activity and UV resistance. The results also suggest that the RA/cAMP-inducible UVDRP in F9 stem cells may be important for the sensitivity or resistance of the cells to UV damage.
authors.affiliation: Department of Biochemistry, Chang Gung Medical College, Taoyuan, Taiwan, ROC.
authors.forename: C C
authors.initials: CC
authors.lastname: Chao
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004249:DNA Damage; D004274:DNA, Recombinant; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000378:metabolism; D010957:Plasmids; D013724:Teratoma; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
chemical_list: D004274:DNA, Recombinant; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins