Discrimination of genotoxic and non-genotoxic hepatocarcinogens by statistical analysis based on gene expression profiling in the mouse liver as determined by quantitative real-time PCR
MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS
Authors: Watanabe, Takashi; Suzuki, Takayoshi; Natsume, Masakatsu; Nakajima, Madoka; Narumi, Kazunori; Hamada, Shuichi; Sakuma, Tomohiro; Koeda, Akiko; Oshida, Keiyu; Miyamoto, Yohei; Maeda, Akihisa; Hirayama, Michiasa; Sanada, Hisakazu; Honda, Hiroshi; Ohyama, Wakako; Okada, Emiko; Fujiishi, Yohei; Sutou, Shizuyo; Tadakuma, Ayami; Ishikawa, Yasuyoshi; Kido, Mahoko; Minamiguchi, Rina; Hanahara, Izumi; Furihata, Chie
Abstract
The general aim of the present study is to discriminate between mouse genotoxic and non-genotoxic hepatocarcinogens via selected gene expression patterns in the liver as analyzed by quantitative real-time PCR (qPCR) and statistical analysis. qPCR was conducted on liver samples from groups of 5 male, 9-week-old B6C3F(1) mice, at 4 and 48 h following a single intraperitoneal administration of chemicals. We quantified 35 genes selected from our previous DNA microarray studies using 12 different chemicals: 8 genotoxic hepatocarcinogens (2-acetylaminofluorene, 2,4-diaminotoluene, diisopropanolnitrosamine, 4-dimethylaminoazobenzene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, N-nitrosomorpholine, quinoline and urethane) and 4 non-genotoxic hepatocarcinogens (1,4-dichlorobenzene, dichlorodiphenyltrichloroethane, di(2-ethylhexyl)phthalate and furan). A considerable number of genes exhibited significant changes in their gene expression ratios (experimental group/control group) analyzed statistically by the Dunnett's test and Welch's t-test. Finally, we distinguished between the genotoxic and non-genotoxic hepatocarcinogens by statistical analysis using principal component analysis (PCA) of the gene expression profiles for 7 genes (Btg2, Ccnf, Ccng1, Lpr1, Mbd1, Phlda3 and Tubb2c) at 4 h and for 12 genes (Aen, Bax, Btg2, Ccnf, Ccng1, Cdkn1a, Gdf15, Lrp1, Mbd1, Phlda3, Plk2 and Tubb2c) at 48 h. Seven major biological processes were extracted from the
Molecular coupling of DNA methylation and histone methylation
EPIGENOMICS
Authors: Hashimoto, Hideharu; Vertino, Paula M.; Cheng, Xiaodong
Abstract
The combinatorial pattern of DNA and histone modifications constitutes an epigenetic 'code' that shapes gene-expression patterns by enabling or restricting the transcriptional potential of genomic domains. DNA methylation is associated with histone modifications, particularly the absence of histone H3 lysine 4 methylation (H3K4rne0) and the presence of H3K9 methylation. This article focuses on three protein domains (ATRX Dnmt3 Dnmt3L [ADD], Cys X X Cys [CXXC] and the methyl-CpG-binding domain [MBD]) and the functional implications of domain architecture in the mechanisms linking histone methylation and DNA rnethylation in mammalian cells. The DNA methyltransferase DNMT3a and its accessory protein DNMT3L contain a H3K4me0-interacting ADD domain that links the DNA methylation reaction with unmodified H3K4. The H3K4 methyltransferase MLL1 contains a CpG-interacting CXXC domain that may couple the H3K4 methylation reaction to unmethylated DNA. Another H3K4 methyltransferase, SET1, although lacking an intrinsic CXXC domain, interacts directly with an accessory protein CFP1 that contains the same domain. The H3K9 methyltransferase SETDB1 contains a putative MBD that potentially links the H3K4 methylation reaction to methylated DNA or may do so through the interaction with the MBD containing protein MBD1. Finally, we consider the domain structure of the DNA methyltransferase DNMT1, its accessory protein UHRF1 and their associated proteins, and propose a mechanism by which DNA methylation and histone methylation may be coordinately maintained through mitotic cell division, allowing for the transmission of parental DNA and for the histone methylation patterns to be copied to newly replicated chromatin.