Investigators may have uncovered the general mechanism that governs RNA polymerase movement, they report in the January 28 issue of Cell.

The finding "provides a framework for understanding how numerous external regulatory signals converge to change the properties of the RNA polymerase active site," co-author Evgeny Nudler of New York University told The Scientist.

Nudler and colleagues explored RNA polymerase's F bridge helix at its elongation complex's catalytic center. In 2001, Roger Kornberg at Stanford University and colleagues suggested the F bridge drives the enzyme forward by switching between its bent and straight conformations.

Using a genetic screen, the researchers isolated two mutations in Escherichia coli RNA polymerase's G loop, a region adjacent to the F bridge that recent studies suggested regulated F bridge conformation. One, G1136S, led to faster elongation as well as rendering RNA polymerase poorly responsive to pauses and terminators. The other, I1134V, rendered...

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