How would an mRNA sequence differ if it were from a prokaryotic cell?

The processing of eukaryotic pre-mRNAs includes modification of both ends of the molecule and the removal of introns from its middle. The 5? end of pre-mRNAs is modified by the addition of a methylated nucleoside, called 7-methylguanosine, linked by a special 5?-5? phosphodiester bond. This process is called capping. The first step is the addition of guanosine-5'-triphosphate in reverse orientation to the 5? terminal nucleotide of mRNA. Then methyl groups are added to this G residue and to the riboses of one or two next nucleotides of the RNA chain. This created 7-methylguanosine cap protects the transcript from exonuclease attack, facilitates RNA splicing and transport from the nucleus to the cytoplasm, as well as aligns eukaryotic mRNAs on the ribosome during protein synthesis].
 
The 3? end of most eukaryotic mRNAs is defined by cleavage of the primary transcript and addition of a poly-A tail in reaction called polyadenylation. The signal for polyadenylation in mammalian cells ? AAUAAA is located 10 to 30 nucleotides upstream of the site of polyadenylation. The enzyme called poly(A) polymerase sequentially adds about 200 adenylate (AMP) residues to the 3? end of mRNA. This pol(A) tail facilitates transport of the mRNA molecules to the cytoplasm, stabilizes some of them in the cytoplasm and may facilitate translation.
 
The most striking modification of pre-mRNAs is the removal of introns in process called splicing. Introns are noncoding sequences which interrupt the coding sequences (exons) of most eukaryotic genes and are precisely excised from the mature mRNA.