sentence: Therefore , 2 ′ CMe monosubstituted NTPs of the four natural ribonucleotide bases ( 2 ′ CMeGTP , 2 ′ CMeATP , 2 ′ CMeCTP , and 2 ′ CMeUTP ) were tested for their inhibition of RNA PolI , PolII , PolIII , and PolRMT .