Stretch a DNA Loop, Turn Off Proteins

Dec 05, 2006
Stretch a DNA Loop, Turn Off Proteins
Photo Credit: Mike White, UCSD

It may look like mistletoe wrapped around a flexible candy cane. But this molecular model shows how some proteins form loops in DNA when they chemically attach, or bind, at separate sites to the double-helical molecule that carries life’s genetic blueprint.

Biologists have discovered that the physical manifestation of DNA loops are a consequence of many biochemical processes in the cell, such as the regulation of gene expression. In other words, these loops indicate the presence of enzymes or other proteins that are turned on. Now physicists at the University of California, San Diego have discovered that stretching the DNA molecule can also turn off the proteins known to cause loops in DNA.

“We showed that certain enzymes acting on DNA could be switched off or on simply by applying a small amount of mechanical tension across the DNA molecule,” said Douglas Smith, an assistant professor of physics at UCSD who headed the team that published the discovery in the December issue of the Biophysical Journal.

“We showed this by mechanically manipulating and stretching single DNA molecules. This switching effect could provide a molecular mechanism for cells to be able to sense and respond to mechanical stresses that they may normally experience. Such stresses could be generated internally by the cells themselves, such as when the cell undergoes changes in shape during the cell cycle, or as external stresses from the environment.”

The amount of tension or stretching that needs to be applied to the molecule is extremely small, Smith added, only one pico-Newton, or one-trillionth of the force generated by the weight of an apple.

Other members of the UCSD team were Gregory Gemmen, a physics graduate student, and Rachel Millin, a laboratory assistant. The study was supported by grants from the Burroughs Wellcome Fund, Kinship Foundation and Arnold and Mabel Beckman Foundation.

Source: UCSD

Explore further: New class of insecticides offers safer, more targeted mosquito control

Related Stories

The genome's 3D structure shapes how genes are expressed

Jun 23, 2013

Scientists from Australia and the United States bring new insights to our understanding of the three-dimensional structure of the genome, one of the biggest challenges currently facing the fields of genomics ...

Unspooling DNA from nucleosomal disks

May 23, 2013

The tight wrapping of genomic DNA around nucleosomes in the cell nucleus makes it unavailable for gene expression. A team of Ludwig-Maximilians-Universitaet (LMU) in Munich now describes a mechanism that allows chromosomal ...

Recommended for you

Scientists discover new 'transformer frog' in Ecuador

4 hours ago

It doesn't turn into Prince Charming, but a new species of frog discovered in Ecuador has earned the nickname "transformer frog" for its ability to change its skin from spiny to smooth in five minutes.

Longer DNA fragments reveal rare species diversity

4 hours ago

A challenge in metagenomics is that the more commonly used sequencing machines generate data in short lengths, while short-read assemblers may not be able to distinguish among multiple occurrences of the ...

Scientists say polar bears won't thrive on land food

4 hours ago

A group of researchers say polar bears forced off melting sea ice will not find enough food to replace their current diet of fat-laden marine mammals such as seals, a conclusion that contradicts studies indicating ...

The vital question: Why is life the way it is?

6 hours ago

The Vital Question: Why is life the way it is? is a new book by Nick Lane that is due out on April 23rd. His question is not one for a static answer but rather one for a series of ever sharper explanations—explanations that a ...

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.