Figure 2.

Mixed A/G tailing by TENT4A/B. RNA polymerase II transcribed mRNA is capped and polyadenylated. The poly(A) tail can be additionally tailed with GMP residues by TENT4A/B proteins. The mixed A/G tail (with 1 G incorporated per 10–20 As) is more resistant to the CNOT complex-mediated deadenylation than the pure poly(A) tail as both CNOT6 L and CNOT7 deadenylases fall off their substrates once they encounter a G (a non-A) residue. Ultimately all mRNAs are degraded from both 5′ and 3′ ends following deadenylation and decapping.