FAQ: Will Poly(U) Polymerase incorporate GTPs onto the 3’ end of an RNA?

Poly(U) polymerase can add a limited number (5 to 20) of G nucleotides to the 3' end of RNA. The length of poly G addition varies with different RNA substrates. In contrast, Poly(A) Polymerase is much more selective, exhibiting a strong preference for ATP compared to rGTP, rCTP or UTP. Few if any G's would be added with poly (A) polymerase.