Mello, Craig Cameron (1960-…), an American biologist, won the 2006 Nobel Prize in physiology or medicine for his discovery of an important method of controlling the activity of genes in living organisms. Mello shared the prize with fellow American biologist Andrew Z. Fire. Their work has applications in the study of how genes function and in the development of treatments for many diseases.
Genes direct the formation, growth, and reproduction of cells and organisms through a process known as gene expression. In this process, a cell makes a protein according to the instructions carried by a gene. These instructions are encoded in a double-stranded, chainlike molecule called DNA (deoxyribonucleic acid). RNA (ribonucleic acid), another chainlike molecule, plays a variety of roles in gene expression. Unlike DNA, RNA usually consists of a single strand. One type of RNA, known as messenger RNA or mRNA, copies chemical instructions from DNA. The mRNA carries the instructions to protein-making cell structures called ribosomes, which use them to make a specific protein.
Biologists had observed that injecting certain types of RNA into the cells of plants interfered with the production of certain proteins within the cells. Mello and Fire experimented with roundworms to study this process in animals. They discovered that injecting double-stranded RNA into the roundworms halted the expression of a specific gene by destroying the mRNA carrying instructions from that gene. They called this process RNA interference. In addition, the scientists showed that the sequence of chemical units making up the double-stranded RNA had to be identical to that of a portion of the affected gene. They found that any gene in the roundworm could be effectively switched off by injecting a double-stranded segment of RNA with a corresponding sequence.
RNA interference occurs naturally in the cells of living organisms, where it often serves as a defense against viruses. Many viruses have double-stranded RNA as their genetic material. RNA interference can protect the cell by halting the expression of genes injected by the virus. Scientists can use RNA interference to stop the expression of a particular gene they wish to study. In this way, they can learn what proteins are produced by specific genes. Scientists are investigating the use of RNA interference to treat diseases caused by viruses, such as hepatitis and AIDS. They are also studying ways to use RNA interference to treat diseases, such as cancer, that involve the abnormal function of genes.
Mello was born in New Haven, Connecticut, on October 18, 1960. He studied biochemistry at Brown University in Providence, Rhode Island, graduating with a B.S. degree in 1982. He received his Ph.D. degree in biology in 1990 from Harvard University. Mello conducted research at the Fred Hutchinson Cancer Research Center in Seattle from 1990 to 1994. In 1994, he became a professor in the molecular medicine program at the University of Massachusetts in Worcester.
See also Cell (Producing proteins) ; Fire, Andrew Zachary RNA .
