<P> Protein coding genes are transcribed into messenger RNAs (mRNAs) that carry the information from DNA to the site of protein synthesis . Although mRNAs possess great diversity, they are not the most abundant RNA species made in the cell . The so - called non-coding RNAs account for the large majority of the transcriptional output of a cell . These non-coding RNAs perform a variety of important cellular functions . </P> <P> Eukaryotes have three nuclear RNA polymerases, each with distinct roles and properties </P> <Table> <Tr> <Td> Name </Td> <Td> Location </Td> <Td> Product </Td> </Tr> <Tr> <Td> RNA Polymerase I (Pol I, Pol A) </Td> <Td> nucleolus </Td> <Td> larger ribosomal RNA (rRNA) (28S, 18S, 5.8 S) </Td> </Tr> <Tr> <Td> RNA Polymerase II (Pol II, Pol B) </Td> <Td> nucleus </Td> <Td> messenger RNA (mRNA), most small nuclear RNAs (snRNAs), small interfering RNA (siRNAs) and microRNA (miRNA). </Td> </Tr> <Tr> <Td> RNA Polymerase III (Pol III, Pol C) </Td> <Td> nucleus (and possibly the nucleolus - nucleoplasm interface) </Td> <Td> transfer RNA (tRNA), other small RNAs (including the small 5S ribosomal RNA (5s rRNA), snRNA U6, signal recognition particle RNA (SRP RNA) and other stable short RNAs </Td> </Tr> </Table> <Tr> <Td> Name </Td> <Td> Location </Td> <Td> Product </Td> </Tr>

Where does mrna processing take place in eurkaryotic cells