18) The enzyme poly-A polymerase is responsible for adding 3' poly-A tails to eukaryotic mRNAs. This enzyme... A. cuts the mRNA after recognition of the cleavage/polyadenylation signal by CstF and CPSF proteins. B. polymerizes the tail using an RNA template that is part of the enzyme. C. isthesameaspolII D. normally adds about 2000 A nucleotides to the mRNA. E. uses A TP as a substrate.

Poly-A Polymerase is an enzyme of the family of the DNA polymerase beta (polβ) family which catalyzes the reaction of the addition of AMP from ATP to the DNA polymerase beta (polβ) family.

ATP+RNA-3'OH--------->Pyrophosphate + RNApA-3'OH.

In this reaction, after the mRNA is cleaved, the Poly-A Polymerase template-independently adds about 200 A nucleotides (from ATP) one by one.