DNA methylation is catalyzed by DNA methyltransferases (DNMT), which transfer the methyl group from the cofactor, S-adenosyl-l-methionine (AdoMet), to the position 5 of the deoxycytidine in a CpG context.[4] Two nucleosides analogues of cytidine, 5-azacytidine 2 (5aza) and 5-azadeoxycytidine 3 (5azadC), have been approved by the US Food and Drug Administration (FDA) for the treatment of myelodysplastic syndromes (MDS) and acute myeloide leukemia (AML).[5]. Here, DNMT1 is linked to myelodysplastic syndrome.