Fig. 1.

Epigenetics regulate the gene expression without alteration in DNA sequence. It mainly consists of DNA methylation, histone modification, non-coding RNA, chromatin remodeling. a The protruding of amino tails of histone modification can undergo several post-translational modifications that affect the expression of genes. Illustrated is the major histone modifications that have been studied in the setting of colorectal cancer such as acetylation, methylation, and phosphorylation. This process is mediated by HATs, HDACs, HMTs, HDMs and protein kinases (PKs). In open chromatin state, histone tail recruits HATs, HMTs, and PKs which can promote gene transcription. In closed chromatin state, histone tail removes these histone-modifying enzymes which can inhibit the gene transcription. (b)