Phillip Allen Sharp

Phillip Allen Sharp
(1944)

American molecular biologist, awarded the 1993 Nobel Prize for Physiology or Medicine, along with Richard J. Roberts, for his independent discovery that individual genes are often interrupted by long sections of DNA that do not encode protein structure.
Sharp received a doctorate in chemistry from the University of Illinois at Urbana-Champaign in 1969. In that year he began working at the California Institute of Technology, moving to the Cold Spring Harbor Laboratory in New York in 1971. In 1974 he went to the Massachusetts Institute of Technology, where he did his prize-winning research. In 1977 Sharp helped found Biogen Ltd., a biotechnology company.

In 1977 Sharp and his team discovered that the messenger RNA (mRNA) of an adenovirus corresponded to four separate, discontinuous segments of DNA. They found that the segments of DNA that coded for proteins, now called exons, were separated by long stretches of DNA, now called introns, that did not contain genetic information. At the same time, a team working independently under Roberts came up with the same finding. Previously biologists had believed that genes were continuous stretches of DNA that served as direct templates for mRNA in the assembly of proteins; this model was based on studies of prokaryotic organisms such as bacteria. Following the discovery of Sharp and Roberts, it was demonstrated that the discontinuous gene structure is the most common one found in eukaryotes, among which are all higher organisms, including human beings.

Subsequent studies, many of them carried out in Sharp's laboratory, showed that DNA transcription initially produces a precursor RNA molecule containing copies of the introns; the final mRNA molecule is produced by the removal of the introns and the splicing together of the exons. A significant proportion of genetic diseases result from mutations that arise during splicing. Biologists also believe that the discontinuous structure of genes may be an evolutionary mechanism, permitting the "reshuffling" of exons and thus the synthesis of new proteins.