Clocking in and out of gene expression

June 14, 2007

A chemical signal acts as time clock in the expression of genes controlled by a master gene called a coactivator, said Baylor College of Medicine researchers in a report that appears in the journal Cell today.

“We have long known that our bodies live by a daily and monthly and even yearly clock and that cells have clocks as well,” said Dr. Bert O’Malley, chair of molecular and cellular biology at BCM and senior author of this report. “We have actually taken this concept to the gene now and said that we are made up of 25,000 genes that have clocks too.” Genes get expressed and carry out their functions through proteins, he said. Gene expression involves the machinery of the cell translating the gene’s code into a protein that carries out function. This process has to have a beginning and an end.

“That sets the time clock,” said O’Malley. “The question is, ‘How is this done?’” The answer lies in coactivators – master genes that turn other genes on and off.

“Inherent to the structure of these coactivators is a clock,” he said. “But the clock needs to be set off.” In studies of breast cancer cells, O’Malley and his colleagues showed how the clock works. Using steroid receptor coactivator-3 (SRC-3), they demonstrated that activation requires addition of a phosphate molecule to the protein at one spot and addition of an ubiquitin molecule at another point. Each time the message of the gene is transcribed into a protein, another ubiquitin molecule is chained on. Five ubiquitins in the chain and the protein is automatically destroyed.

“It’s built-in self destruction,” said O’Malley. “It prevents you from activating a potent factor in the cells that just keeps the clock running and the gene continuing to be expressed.” In that scenario, the result could be cancer, too much growth or an abnormal function.

“It means there’s a fixed length of time that the molecule can work. When it’s activated, it’s already preprogrammed to be destroyed. The clock’s running and each time an ubiquitin is added, it is another tick of the clock.” When the clock system fails, problems result.

“If you can’t start the clock, you can’t stop the clock. If you stop the clock before you should or if it is running too slow or too fast, it causes problems in the cells,” he said.

Source: Baylor College of Medicine

Explore further: Dietary restriction gives fruit flies a rhythm for a long life

Related Stories

Tomato domestication decelerated the circadian clock

November 20, 2015

All organisms, from bacteria to humans, exhibit endogenous rhythms controlled by the circadian clock. These rhythms are important for synchronization with the environment. Scientists at the Max Planck Institute for Plant ...

Time travel with the molecular clock

November 23, 2015

Migration isn't a new phenomenon, but new insights suggest that modern-day Europeans actually have at least three ancestral populations. This finding was published by Johannes Krause and prominently featured on the cover ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Machine Translates Thoughts into Speech in Real Time

December 21, 2009

( -- By implanting an electrode into the brain of a person with locked-in syndrome, scientists have demonstrated how to wirelessly transmit neural signals to a speech synthesizer. The "thought-to-speech" process ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.