Where in a cell does RNA processing occur?
RNA processing primarily occurs in the nucleus (there are some exceptions but they are few and far between, for instance there are some cytoplasmic RNA-processing foci in certain strains of yeast, and these are called P-bodies, and for the most part these ‘processing’ sites that are in cytoplasm are more concerned with the destruction of RNA, as opposed to the processes that you have listed which are involved in the maturation of an RNA molecule to enable it to carry out its function). Splicing, capping and polyadenylation are carried out by distinct enzyme-complexes that actually associate with the RNA polymerase enzyme in the nucleus, as it is in the process of transcribing a gene. Splicing is performed by the Spliceosome (pronounced “splice-o-some”). This is a huge complex that not only splices the pre-mRNA molecules but also prohibits the mRNA from leaving the nucleus until all the splicing reactions have taken place. Capping involves the addition of a 7-methyl-guanosine residue to
