DksA polices the intersection of replication and transcription

May 13, 2010

DNA replication, the process by which a strand of DNA is copied during cell proliferation , and DNA transcription, the process by which the message in the DNA is translated into messenger RNA, involve the same "track" or DNA template. What happens when the two mechanisms are on the same track at the same time? Baylor College of Medicine researchers have identified the director -- the transcription factor DksA. A report appears in the current issue of the journal Cell.

Dr. Jue D. (Jade) Wang, assistant professor of molecular and at Baylor College of Medicine, focuses her attention on replication - the process by which a strand of DNA is copied during (growth and division).

Dr. Christophe Herman, also an assistant professor of molecular and human genetics at BCM, zeroes in on transcription - the process by which the message in the DNA is translated into and ultimately the proteins that are workhorses of the cell.

Scientists in the two fields rarely communicate, but the two processes involve the same "track" or DNA template.

"What happens when two machines are on the same track but going in opposite directions?" said Wang. "These two processes are happening at the same time and use the same template."

The two laboratories combined their skills to answer that question and came up with a director -- the transcription factor DksA. A transcription factor is a protein that helps regulates expression (or the level) of , the researchers

A report on their work appears in the current issue of the journal Cell.

"We think this factor is one of the reason there are not more traffic jams," said Wang. "It is there to make sure that the traffic flows."

Their experiments show that DksA acts on the process of transcription directly to prevent conflict between transcription and replication.

"The factor began our collaboration," said Herman. "We saw that it was regulating the process of transcription. It also tags along with RNA (the enzyme that prompts the process of making a strand of RNA from the DNA strand)."

When it sees the DNA polymerase (an enzyme critical to replication) come along, "it removes the RNA polymerase from the track," said Herman. That allows replication to take place and prevents the two "machines" from colliding.

The two did their work in a form of Escherichia coli (E. coli), a bacterium often used as a model organism in the laboratory. When DksA was not present in the bacteria, the cell was unstable, prompting a DNA damage response from halted replication.

"Stress can promote endogenous DNA damage," said Herman. Starvation is one method of such stress, he said. When DksA is present, it prevents disruption of replication and maintains the integrity of the DNA.

Previously, it was thought that the DNA polymerase simply knocked the RNA polymerase out of the way, said Herman.

"That is not the case. You need to have specific factors to remove the RNA polymerase," he said.

The findings raise as many questions as they answer, said Wang. Does the factor work before or after the enzymes collide?

"We don't know the mechanism yet," she said.

Explore further: The origins of polarized nervous systems

More information: www.cell.com/

add to favorites email to friend print save as pdf

Related Stories

Scientists crash test DNA's replication machinery

Feb 10, 2010

(PhysOrg.com) -- Important molecular machines routinely crash into one another while plying their trades on DNA. New research shows that the enzymes that copy DNA before cell division, called replisomes, are the kings of ...

Copy number variation may stem from replication misstep

Dec 27, 2007

Genome rearrangements, resulting in variations in the numbers of copies of genes, occur when the cellular process that copies DNA during cell division stalls and then switches to a different genetic “template,” said researchers ...

Recommended for you

The origins of polarized nervous systems

1 hour ago

(Phys.org)—There is no mistaking the first action potential you ever fired. It was the one that blocked all the other sperm from stealing your egg. After that, your spikes only got more interesting. Waves ...

New fat cells created quickly, but they don't disappear

5 hours ago

Once fat cells form, they might shrink during weight loss, but they do not disappear, a fact that has derailed many a diet. Yale researchers in the March 2 issue of the journal Nature Cell Biology descri ...

A single target for microRNA regulation

6 hours ago

It has generally been believed that microRNAs control biological processes by simultaneously, though modestly, repressing a large number of genes. But in a study published in Developmental Cell, a group ...

Sizing up cells: Study finds possible regulator of growth

21 hours ago

Modern biology has attained deep knowledge of how cells work, but the mechanisms by which cellular structures assemble and grow to the right size largely remain a mystery. Now, Princeton University researchers ...

User comments : 0

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.