Figure 4.

Several epigenetic mechanisms can lead to altered gene expression in tumor cells. (A) Histone acetylation results in tightly wound chromatin and inaccessibility of transcription factors to DNA; (B) Histone deacetylation and chromatin remodeling complexes promote the unwinding of chromatin complexes, allowing for transcriptional upregulation; (C) DNA can be methylated on C and G residues, which can lead to transcriptional repression; (D) Following transcription initiation by RNA polymerase II (Pol II), miRNAs can prevent protein translation by either blocking translocation of ribosomes down the mRNA transcript or by directing mRNA degradation.