Pre-mRNAs in eukaryotic cells undergo three main processing steps: Capping at the 5' end, the addition of a poly(A) tail at the 3' end, and splicing to remove introns. Which of the following statements about these steps is/are correct?
(i) The enzyme cap Mtase catalyzes the production of diphosphate 5'end.
(ii) Apart from the AAUAAA signal sequence, the UGUA signal sequence can also direct cleavage and polyadenylation.
(iii) The splicing reaction is catalyzed by the spliceosome.