Figure 1.

Schematic view of the interplay between epigenetic mechanisms. The transcription of the coding regions of the protein-coding genes originates, after a splicing and maturation of precursors, mature mRNAs that lead the synthesis of the protein chains on the ribosomes. DNA methyltransferases (DNMTs) are a family of enzymes that methylate cytosines in CpG dinucleotides. The methylation/demethylation of CpGs influences gene expression by several mechanisms including changing the binding of transcription factors and the interaction with other enzymes that, in turn, modify histone tails. Chemical modifications of histones (such as methylation and acetylation) influence chromatin conformation and the binding of protein complexes needed for gene transcription. Long noncoding RNAs (lncRNAs) may modulate the activity of DNMTs and interact with the histone machinery. Precursors of microRNAs (miRNAs) are transcribed and processed into mature miRNAs. These miRNAs bind to mRNAs bearing in their 3′ untranslated region sequences complementary to the miRNAs. The binding of miRNAs to their targets mRNAs can stop protein translation or even induce the degradation of the mRNA. Some lncRNAs may also modulate the stability of miRNAs. These, in turn, appear to modulate the transcription of some lncRNA. Thick arrows represent DNA-encoded RNA transcription and RNA-encoded protein translation. Thin arrows represent direct or indirect interactions.