Methylation, of genes

But it is not so simple or clear, and some mutations seem irrelevant to the process and outcome. For example, it seems there is collaboration of mutant cellular genes. There are also some epigenetic steps such as hypomethylation and methylation of gene promoters. 

Pereira, MM Medical College of Ohio Effect of peroxisome proliferators on methylation of genes NIEHS... 

Histone tails are the N-terminal regions of histones which reach outside the nucleosomes. They are not essential for the formation in of nucleosomes but are required for the formation of higher-order chromatin structures. The histone tails are also known to be heavily posttranslationally modified by acetylation, phosphorylation, methylation, etc. and are important for the regulation of gene activity. 

Methylation of histones is correlated with activation and repression of gene transcription. 

Plasmid- or transposon-mediated resistance common to the MLS group is due to RNA methylase genes emiA, emiB and ermC) which code for the methylation of an adenine residue in 23 S rRNA. Methylation prevents the drugs from binding to the 508 ribosomal subunit and confers resistance to all MLS antibiotics. 

DiziK M, CHRISTMAN J K andwAiNFAN E (1991) Alterations in expression and methylation of specific genes in livers of rats fed a cancer promoting methyl-deficient diet . Carcinogenesis, 12, 1307-12. 

Bastian, PJ, J Ellinger, LC Heukamp, P Kahl, SC Muller, and A von Rucker. 2007. Prognostic value of CpG island methylation of PTGS2, RAR-beta, EDNRB, and other gene loci in patients undergoing radical prostatectomy. Eur Urol 51(3) 665—674. 

King-Batoon, A, JM Leszczynska, and CB Klein. 2008. Modulation of gene methylation by genistein or lycopene in breast cancer cells. Environ Mol Mutagen 46 36 -5. 

Bestor, T. (1990), DNA methylation evolution of a bacterial immune function into a regulator of gene expression and genome structure in higher eukaryotes , Philosophical Transactions of the Royal Society of London, Series B, 326 179- 187. 

---