INHIBITION OF MURINE DNA METHYLTRANSFERASE Dnmt3a BY DNA DUPLEXES CONTAINING PYRIMIDINE-2(1H)-ONE
The inhibition of the catalytic domain of Dnmt3a methyltransferase (Dnmt3a-CD) by DNA duplexes containing mechanism-based inhibitor pyrimidine-2(1H)-one (P) instead of the target cytosine has been studied. It has been shown that conjugates of Dnmt3a-CD with P-DNA are not stable to heating at 65° in 0.1% SDS. The yield of covalent intermediate increases in the presence of the regulatory factor Dnmt3L. The DNA minor groove is important for covalent intermediate formation during the methylation reaction catalyzed by Dnmt3a-CD. P-DNA was shown to inhibit Dnmt3a-CD, the IC<sub>50</sub> being 830 nM. The competitive mechanism of inhibition of Dnmt3a-CD by P-DNA has been elucidated. It is suggested that therapeutic effect of zebularine could be achieved by inhibition not only of Dnmt1 but also Dnmt3a.