Most Valuable Player: RNA Polymerase Fulfills More Than One Role. In addition to elongating messenger RNA, RNA polymerase takes part in a number of key tasks, such as editing and chain shortening. Pausing is the likely first step on any of these alternative pathways.

It almost sounds like the setup to a punch line: How is reading a gene like playing baseball? But the answer is no joke. Just as baseball players stop at first, second, or third base on their sprint toward home plate, the molecules called RNA polymerases frequently pause at certain places along the DNA in the process of transcribing a gene.

Now, using a new technique, HHMI predoctoral scholar Kristina Herbert, working in Steven Block's lab at Stanford University, and her colleagues have pinpointed where on the double helix individual molecules hesitate in the act of transcription. In fact, certain places in the DNA underfoot seem to signal those mystery stops, they reported in the June 16, 2006, issue of Cell.

The excitement about the study has as much to do with the technological advance as it does with the finding.

"This is a major accomplishment," says Peter von Hippel, a chemistry professor at the University of Oregon, who wrote an accompanying commentary on the paper. "The job of the transcription complex is to read the sequence. You have to know exactly where you are on the [DNA] template in order to interpret the biological consequences of being there."

Image Adapted by permission from Macmillan Publishers Ltd: Grieve, S.J. and Von Hippel, P.H. 2005. Nat. Rev. Mol. Cell Biol. 6, 221-232 and Elsevier: von Hippel, P.H. 2006. Cell 125, 1027-1029.

	PAGE 1 OF 2	Continue