Scientists at Berkeley have reported the first direct observations of what happens when the message of a gene is being read during the actual transcription of single DNA molecules. Using a unique experimental setup they designed themselves, the researchers followed transcription by single molecules of RNA polymerase (RNAP), the enzyme responsible for reading the genetic message in humans and other higher organisms as well as bacteria. Their observations provide new insights into how genetic expression in cells may be regulated.
Carlos Bustamante, a biophysicist who holds a joint appointment with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley (UC Berkeley), heads the group that published the results of this work in the March 31 issue of the journal Science. In addition to Bustamante, the other authors were John Davenport and Gijs Wuite with UC Berkeley and Robert Landick with the University of Wisconsin at Madison.
"Our studies reveal that RNAP molecules possess different intrinsic transcription rates and different propensities to pause and stop," the authors state in their paper. "The conformational metastability of RNAP revealed by this single-molecule study of transcription has direct implications for the mechanisms of gene expression in both bacteria and eukaryotes."
The genetic messages stored within the DNA inside the nucleus of a living cell are read by the RNAP enzyme and transcribed into messenger RNA (mRNA) which then carries the information out of the nucleus and into the cytoplasm where protein assembly takes place. RNAP transcribes a gene by tightly clamping itself to the DNA and elongating-growing out-over the gene's base-pairs, catalyzing the creation of an mRNA template in the process.
Previous studies have shown that this elongational growth/transcription is discontinuous; the RNAP may pause at various points along the way for a few seconds or a few
Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory