James Darnell approached the problem of protein regulation from two directions: the cell's mechanisms for processing messenger RNA (mRNA) after transcription but before translation, and the relationship between extracellular signaling molecules and protein expression. Together with German-born biochemist and molecular biologist Klaus Scherrer (1936-) and American virologist Harriet Latham (now Robinson, 1938-), Darnell found the first example of RNA processing in ribosomal RNA (rRNA) in 1961. Although the final ribosome consists of two separate RNA macromolecules, the rRNA is transcribed as a single long molecule that is afterwards cut into two segments. Darnell then turned to the process by which heterogeneous nuclear RNA (hnRNA, the assortment of unprocessed non-ribosomal RNA found in the nucleus) becomes finished mRNA. Darnell and his colleagues discovered various steps necessary to maintain the mRNA in the cytoplasm, including the attachment of a polyadenine sequence at the 3' end of the mRNA and a methylated...