Mdm2 has been identified as a p53 interacting protein that represses p53 transcriptional activity. This suggests that specific histone site acetylation has a regulatory role in gene transcriptional activation. Insulin biosynthesis is regulated by transcriptional and translational levels. Mediator is a multiprotein complex that functions as a transcriptional coactivator in all eukaryotes. It can also act as a transcriptional repressor. Positive regulation depends on TSH, which acts by transcriptional and posttranslational mechanisms. Iron is necessary for the upregulation of transcriptional elements for cell replication and repair. Monomethylated H4K20 (H4K20me1) is involved in the compaction of chromatin and therefore transcriptional repression. Transcription termination has also emerged as an important area of transcriptional regulation. ACAT1 is regulated at both transcriptional and translational levels. The gene order is therefore a simple but effective form of transcriptional regulation. E-box binding proteins play a major role in regulating transcriptional activity. It is regulated by feedback inhibition in the form of transcriptional attenuation. In turn, deacetylated histones are associated with transcriptional repression. This three-dimensional genome structure plays a significant role in transcriptional regulation.