title: Deregulation of DNA methyltransferases and loss of parental methylation at the insulin-like growth factor II (Igf2)/H19 loci in p53 knockout mice prior to tumor development.
abstract: To ascertain whether p53 deficiency in vivo leads to the deregulation of DNA methylation machinery prior to tumor development, we investigated the expression profile of DNA methyltransferases in the thymus and the liver of p53(+/+), p53(+/-), and p53(-/-) mice at 7 weeks of age before tumor development. The expression of DNA methyltransferases was examined in the thymus at 7 weeks of age, since the malignant T-cell lymphoma develops most frequently in p53(-/-) mice around 20 weeks of age. Both mRNA and protein levels of Dnmt1 and Dnmt3b were increased in the thymus and the liver of p53-deficient mice. The expression of Dnmt3a was also increased in the liver but not in the thymus of p53-deficient mice. Dnmt3L expression was reduced in the thymus of p53(+/-) and p53(-/-) mice. The total 5-methylcytosine (5-MeC) in the genomic DNA of p53(+/+), p53(+/-), and p53(-/-) mice was quantitated by dot-blot using antibody against 5-MeC. Global methylation was increased in the thymus and the liver of p53-deficient mice. To correlate the deregulated expression of DNA methyltransferases with the disturbance of the epigenetic integrity, we examined the DNA methylation of the imprinting control region (ICR) at the insulin-like growth factor II (Igf2)/H19 loci in the thymus and the liver of p53(+/+), p53(+/-), and p53(-/-) mice. The region containing two CCCTC binding factor (CTCF) binding sites in the 5'-ICR tended to be hypomethylated in the thymus of p53(-/-) mice, but not in the liver. The expression profile of Igf2 and H19 indicated that the thymus-specific changes of Igf2 and H19 expression were coherent to the hypomethylation of the ICR in the thymus. Our results suggest that p53 is required for the maintenance of DNA methylation patterns in vivo.
authors.affiliation: Department of Biological Sciences, 373-1 Gusung-Dong, Korea Advanced Institute of Science and Technology, Yusung-Gu, Taejon 305-701, Republic of Korea.
authors.forename: In Young
authors.initials: IY
authors.lastname: Park
authors.forename: Bo Hwa
authors.initials: BH
authors.lastname: Sohn
authors.forename: Jung Ha
authors.initials: JH
authors.lastname: Choo
authors.forename: Cheol O
authors.initials: CO
authors.lastname: Joe
authors.forename: Je Kyung
authors.initials: JK
authors.lastname: Seong
authors.forename: Young Ik
authors.initials: YI
authors.lastname: Lee
authors.forename: Jae Hoon
authors.initials: JH
authors.lastname: Chung
mesh_terms: D000818:Animals; D001483:Base Sequence; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000378:metabolism*; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000235:genetics*; D016158:Genes, p53; D007335:Insulin-Like Growth Factor II / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; C094335:H19 long non-coding RNA; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D007335:Insulin-Like Growth Factor II; D015254:DNA Modification Methylases