Mechanisms
DNA Methylation
Histone Modification
Epigenetic Tags
Epigenetic tags determine which genes are turned on or off. Many factors incorporate with epigenetic tags, such as: dietary habits, regular activity, and lifestyle. Or in other words, what you eat, your fitness, how you live, if you smoke, or even what kinds of medication you take. These tags are marked all over the genome, and connects the it to the outside environment. Chemical tags mark themselves on two certain occurrences: DNA Methylation and Histone Modification. DNA methylation is a direct change in your DNA, while histone modification is more indirect. (​​4​​​1)
One of many histone modifications, histone acetylation has been assumed to lead to changes in the folding of the nucleosomal fiber (19). This causes the transcription machinery to be able to access promoters and initiate transcriptions more frequently (19). In recent studies, the role of histone acetylation has been suggested to be important in the processes of regulating the structure and fuction of chromatin (21). In histone acetylation, as the name suggests, an acetyl group (COCH3) is added (20). It plays an important role in whether or not a gene is expressed. Histone acetyltransferases, or HATs, are enzymes known for causing the addition of an acetyl group (20). HATs come in two forms, cytoplasmic and nuclear (21). The one associated with transcription and other DNA-dependent process is the nuclear HATs (21).
DNA methylation is a type of DNA modification through chemical changes. Changes can be added or removed without altering the DNA sequence or genetic blueprint code. This process occurs through the addition or removal of a methyl group to the DNA at CpG dinucleotdies. It usually occurs during development to turn on and off certain genes at certain times within the developing embryo. DNA methylation is also involved in X-chromosome inactivation, imprinting, and suppressing certain genes. (15)