Thymidylate Synthase

Thymidylate synthase (TSase) is a key enzyme in cell proliferation as it catalyzes a reaction essential for DNA replication, a reductive methylation of 2′-deoxyuridine-5′-monophosphate (dUMP) to form 2′-deoxythymidine-5′-monophosphate (dTMP) using the co-substrate N5,N10-methylene-5,6,7,8-tetrahydrofolate (CH2H4F).

The activity and expression of TSase are tightly controlled throughout the cell cycle, particularly at the translational level. The TSase protein itself binds to the TSase mRNA both at the translational start site (TSS) and in the coding region, inhibiting translational processing of the message. TSase can also bind to the mRNA of at least nine other important gene products, including those of p53 and c-myc. Therefore, manipulating the level of the TSase protein could induce a cascade of consequential effects on cell growth. Because of its importance in DNA precursor synthesis and repair, TSase has proved to be an important target for many chemotherapeutic and antibiotic drugs. Structural analogs of dUMP (e.g., fluoropyrimidines) and CH2H4F (e.g., antifolates) are well-established drugs targeting thymidylate synthase.