The results of the analysis revealed some interesting structural differences between Pol I and the related RNA polymerase II (Pol II), which is responsible for the synthesis of the messenger RNAs that act as the immediate blueprints for protein synthesis. Cramer had determined the structure of Pol II in the year 2000, while he was a postdoc at Stanford University in California.
An open-and-shut case
Among other things, Pol I differs from Pol II in having several extra elements in its active center, which are involved in the regulation of the enzyme. By modulating the form of the entrance to the active site (which lies in a deep cleft) they enable it to adopt an "open" or a "closed" conformation. It turns out that the enzyme is inactive in the "open" state. The researchers suggest that this phenomenon allows Pol I activity to be inhibited, thus preventing uncontrolled cell growth and proliferation. It is conceivable that this mechanism might serve as a target for the development of new drugs that could retard the growth of tumors. Thus the new structure could point the way to novel agents for the treatment of cancer.
"With this conformational switch between inactive and active states, we appear to have stumbled on a general mechanism that regulates the expression of genetic information in the cell," Cramer says. He and his associates will now turn their attention to the probl
|Contact: Luise Dirscherl|