title: Demethylation of (Cytosine-5-C-methyl) DNA and regulation of transcription in the epigenetic pathways of cancer development.
abstract: Cancer cells and tissues exhibit genome wide hypomethylation and regional hypermethylation. CpG-methylation of DNA ((Me)CpG-DNA) is defined as the formation of a C-C covalent bond between the 5'-C of cytosine and the -CH(3) group of S-adenosylmethionine. Removal of the sole -CH(3) group from the methylated cytosine of DNA is one of the many ways of DNA-demethylation, which contributes to activation of transcription. The mechanism of demethylation, the candidate enzyme(s) exhibiting direct demethylase activity and associated cofactors are not firmly established. Genome-wide hypomethylation can be obtained in several ways by inactivation of DNMT enzyme activity, including covalent trapping of DNMT by cytosine base analogues. Removal of methyl layer could also be occurred by excision of the 5-methyl cytosine base by DNA glycosylases. The importance of truly chemically defined direct demethylation of intact DNA in regulation of gene expression, development, cell differentiation and transformation are discussed in this contribution.
authors.affiliation: Cancer Epigenetics Research, Kalyani (B-7/183), Nadia, West Bengal, India. skpatra_99@yahoo.com
authors.forename: Samir Kumar
authors.initials: SK
authors.lastname: Patra
authors.forename: Aditi
authors.initials: A
authors.lastname: Patra
authors.forename: Federica
authors.initials: F
authors.lastname: Rizzi
authors.forename: Tapash Chandra
authors.initials: TC
authors.lastname: Ghosh
authors.forename: Saverio
authors.initials: S
authors.lastname: Bettuzzi
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D005786:Gene Expression Regulation; D006801:Humans; D009369:Neoplasms / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D004248:DNA (Cytosine-5-)-Methyltransferases