Ciechanover, << chee HAH noh vuhr, >> Aaron (1947-…), an Israeli biochemist, won a share of the 2004 Nobel Prize in chemistry for his research into a process that living cells use to break down proteins. The prize was also awarded to the biochemists Avram Hershko of Israel and Irwin A. Rose of the United States. The three scientists studied a protein called ubiquitin. They discovered that ubiquitin can become attached to unwanted proteins inside the cell. Cellular structures called proteasomes then recognize this ubiquitin “tag” and destroy the unwanted proteins.
In a series of experiments during the late 1970’s and early 1980’s, Ciechanover, Hershko, and Rose determined how cells use ubiquitin to mark unwanted proteins. Their experiments showed that the process involves three major types of enzymes, which they referred to as E1, E2, and E3. First, an E1 enzyme attaches to ubiquitin and prepares it to bond with the unwanted protein. It then transfers the ubiquitin to an E2 enzyme. An E3 enzyme binds to the E2 enzyme and the unwanted protein and helps transfer the ubiquitin from the enzyme to the protein. This process repeats until a chain of several ubiquitins has been attached to the unwanted protein.
When the unwanted protein approaches a proteasome, the ubiquitin tag causes the opening of the proteasome to change shape. This enables the protein to enter the proteasome, where it is broken down. The ubiquitin is removed and returned to the cell to be used again.
Cells can produce hundreds of different E3 enzymes, each of which binds to different proteins. In this way, cells use ubiquitin to target specific proteins for destruction. Ciechanover, Hershko, and Rose’s work has helped scientists working to develop a new class of medicines for a variety of diseases, including cervical cancer and cystic fibrosis. These medicines target the ubiquitin binding process to stimulate the destruction of harmful proteins or to prevent the breakdown of necessary proteins.
Ciechanover was born in Oct. 1, 1947, in Haifa, Israel. In 1974, he earned an M.D. degree from the Hebrew University Hadassah Medical School in Jerusalem. From 1974 to 1977, he served in the Israel Defense Forces. Ciechanover earned a Ph.D. in medicine from the Technion-Israel Institute of Technology in Haifa in 1981. From 1981 to 1984, he conducted research at the Massachusetts Institute of Technology in Cambridge. He then joined the department of biochemistry at the Technion as a lecturer. He became a professor there in 1987.
