In a eukaryotic cell, an enzyme 'X' synthesizes an RNA molecule that subsequently undergoes the addition of methyl guanosine triphosphate at its 5'-end and adenylate residues at its 3'-end. Identify the enzyme 'X'.

Step-by-step solution

The addition of methyl guanosine triphosphate at the 5'-end (capping) and adenylate residues at the 3'-end (tailing) are post-transcriptional modifications specific to heterogeneous nuclear RNA (hnRNA). In eukaryotes, hnRNA is the precursor of mRNA and is transcribed by RNA polymerase II. RNA polymerase I transcribes rRNAs (28S, 18S, 5.8S), and RNA polymerase III transcribes tRNA, 5S rRNA, and snRNAs, which do not undergo this specific capping and polyadenylation process. Poly A polymerase is the enzyme responsible