The findings, based on lab experiments conducted at Cal Tech and computer models developed at Johns Hopkins, are reported in the Nov. 8 issue of the journal "Science."
Scientists have known that living cells send messages from their surfaces to their nuclei by setting off a chain of chemical reactions that pass the information along like signals traveling over a telephone wire. Such reaction chains are called signaling pathways. But while studying one such reaction chain called the NF-kappaB pathway within mouse cells, the university researchers learned that the signal transmission process is even more complicated.
"We found that if the pathway was activated for a short time, a single pulse of activity was delivered to the nucleus, like a single tick of a clock, activating a set of genes," said Andre Levchenko, assistant professor in the Department of Biomedical Engineering at Johns Hopkins. "But longer activation could produce more pulses and induce a larger gene set. We believe that the timing between pulses is critical. If too much or too little time elapsed, the genetic machinery would not respond properly."
Levchenko, a lead author on the "Science" paper, and his colleagues concluded that the signaling pathway inside a cell was serving as much more than a simple wire. "It was not just carrying the information, it was processing it," he said. "The pathway was operating like a clock with a pendulum, delivering the signal at particular intervals of time in a way that could resonate with the behavior of the genes in the nucleus."