5-Azacytidine

Overview
5-Azacytidine is a chemical analogue of cytidine, a nucleoside present in DNA and RNA. Cells in the presence of 5-azacytidine incorporate it into DNA during replication and RNA during transcription. The incorporation of 5-azacytidine into DNA or RNA inhibits methyltransferase thereby causing demethylation in that sequence, affecting the way that cell regulation proteins are able to bind to the DNA/RNA substrate. Inhibition of DNA occurs through the formation of stable complexes between the molecule and with DNA methyltransferases, thereby saturating the cells methylation machinery.

5-azacytidine and its deoxy derivative decitabine (also known as 5-aza-2'deoxycytidine) were first synthesized in Czechoslovakia as potential chemotherapeutic agents for cancer.

It can be used in vitro to remove methyl groups from DNA. This may weaken the effects of gene silencing mechanisms that occurred prior to the methylation. Methylation events are therefore believed to secure the DNA in a silenced state. Demethylation may reduce the stability of silencing signals and thus confer relative gene activation. 5-azacytidine is mainly used in the treatment of myelodysplastic syndrome. It is marketed as Vidaza.