All the genetic information contained in DNA is silent, said Roger Kornberg, PhD, the Mrs. George A. Wizner Professor in Medicine and professor of structural biology. What gives it a voice is RNA polymerase, the enzyme that copies DNA into RNA through a process called transcription. Along with more than a dozen helper molecules, RNA polymerase determines which proteins are produced within a cell. But before scientists can understand the transcription process, they must first unveil the inner structure of RNA polymerase.
Kornberg's lab has been studying RNA and the enzyme that makes it for more than 20 years. Past studies from the lab have shown that the machinery of the RNA polymerase system is in three layers. Kornberg's group published groundbreaking findings in 2001 outlining the structure of the innermost layer. The two current papers focus on the middle layer, which contains many of the helper molecules.
To see the structure of the protein layers, the group passed extremely bright X-rays - generated at the Stanford Synchrotron Radiation Laboratory, or SSRL - through a crystallized version of the proteins. The crystal scatters the X-rays, generating a distinctive diffraction pattern that reveals the sample's three-dimensional atomic structure.
Part of their current work looked at RNA polymerase along with one of the five helper molecules, called transcription factors, in the middle layer. From the structure that could be seen when just a single transcription factor was added, the team extrapolated a picture of the entire middle layer, which,
Contact: Mitzi Baker
Stanford University Medical Center