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Epigenetic control of cell fate and behavior
Published in David M. Gardiner, Regenerative Engineering and Developmental Biology, 2017
Although the specific methylation of key promoters can lead to silencing of tumor-suppressor genes in cancer, the global hypomethylation must also be considered. By removing suppressive methylation marks, the cell is presumably able to express a larger repertoire of gene products, some of which may be outside of the program for that particular source cell type, which could lead to the adoption of different cell identities. Again, the specific role of the target gene is ultimately the most important factor. Demethylation may allow genes to be expressed more readily, but the newly expressed gene may further serve to activate, or repress, its target pathway.
Selenium in soil-microbe-plant systems: Sources, distribution, toxicity, tolerance, and detoxification
Published in Critical Reviews in Environmental Science and Technology, 2022
Anamika Kushwaha, Lalit Goswami, Jechan Lee, Christian Sonne, Richard J. C. Brown, Ki-Hyun Kim
Methylation of Se is the primary process for Se volatilization from the soil (Lin & Terry, 2003). In soil, Se methylation takes place mostly through biological routes to yield less-toxic and volatile derivatives of Se (Vriens et al., 2016). Reaction rates are governed by the species present, microbial activity, OM, and various environmental conditions (e.g., temperature and soil water content). The presence of SeO32− in the soil can help increase the contents of Se in plant system. However, the Se levels do not accumulate in the soil because it is likely lost via volatilization. Selenide undergoes methylation reactions as follows: H2Se → CH3SeH → (CH3)2Se → (CH3)3Se+. However, end product of the methylation reaction is dimethyl selenide instead of trimethylselenomium (Ohta & Suzuki, 2008). Demethylation process is the removal of a methyl group and occurs under oxic and anoxic conditions.
Benzo[a]pyrene osteotoxicity and the regulatory roles of genetic and epigenetic factors: A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Jiezhang Mo, Doris Wai-Ting Au, Jiahua Guo, Christoph Winkler, Richard Yuen-Chong Kong, Frauke Seemann
DNA methylation, closely associated with transcriptional silencing, presents at the 5′ position of the cytosine ring within CpG dinucleotides of DNA. It is catalyzed by DNA methyltransferases (DNMTs) that include DNMT1, DNMT3A and DNMT3B (Chen & Zhang, 2020). Passive demethylation occurs via the suppression of DNA methylation maintenance during DNA replication, while active DNA demethylation is achieved by a methylcytosine-to-hydroxymethylcytosine conversion and a follow-up base excision repair, catalyzed by the ten eleven translocation (TET) gene family members (Guo et al., 2011).