Featured Research

from universities, journals, and other organizations

"Nanocircles" Act As Trojan Horse To Shut Down Disease-Causing Genes, Study Finds

Date:
January 25, 2002
Source:
Stanford University
Summary:
Stanford scientists have synthesized a molecule of DNA that is capable of shutting off specific genes in living bacteria. Dubbed the “nanocircle,” the new nanometer-size molecule might one day give researchers the ability to target harmful genes that cause cancer and other diseases in humans.

Stanford scientists have synthesized a molecule of DNA that is capable of shutting off specific genes in living bacteria. Dubbed the “nanocircle,” the new nanometer-size molecule might one day give researchers the ability to target harmful genes that cause cancer and other diseases in humans.

“In the long range, we hope that nanocircles could be used for genetic therapy in people,” said Eric T. Kool, a professor of chemistry at Stanford who led the nanocircle study.

The results were published in the Jan. 8 issue of the Proceedings of the National Academy of Sciences (PNAS) in a paper co-authored by Kool, former postdoctoral fellow Tatsuo Ohmichi and graduate student Angιle Maki.

Rolling circles

Kool helped pioneer nanocircle technology in 1991 while at the University of Rochester, where he synthesized the first circular DNA molecules capable of replicating themselves in a test tube when combined with special DNA-copying enzymes and other chemicals.

The technique – known as “rolling circle amplification” – is now one of the hottest fields in biotechnology, because it offers the potential to produce and detect more copies of a specific DNA sequence faster and cheaper than other methods.

“What is new about the PNAS study is that, for the first time, we used a nanocircle in a living cell – the bacterium E. coli,” Kool noted.

He and his colleagues wanted to see if a synthetic molecule of circular DNA could target a specific gene in E.coli. To do that, they needed to design a DNA nanocircle that could duplicate large numbers of ribozymes – enzymes found in all living cells that are capable of altering the function of individual genes in the organism’s DNA. Ribozymes are made of RNA – protein-producing molecules manufactured by genes.

“Ribozymes are biologically active,” Kool said. “They can inhibit or shut down a gene by destroying its RNA.”

In nature, ribozymes are assembled by DNA molecules, which act as templates. First, the DNA binds with an enzyme called RNA polymerase, then the ribozyme is formed. The challenge for researchers was to figure out which synthetic nanocircle was best suited for binding with the naturally existing RNA polymerase in the bacterial cell.

“RNA polymerases are picky, so the real trick was making a nanocircle that was especially good,” Kool noted. “We said, ‘Let’s let the RNA circles tell us which polymerase they like best – let them tell us who the winner is, and then we’ll know which circle is best.’”

The researchers ended up making 15 generations of nanocircles until they finally came up with the best DNA sequence.

“It was evolution in a test tube,” Kool recalled.

The chosen nanocircles were then added to the E. coli to determine if the mixture would produce ribozymes capable of cleaving a specific drug-resistant gene in the bacteria.

The results were clear: The targeted gene stopped functioning more than 90 percent of the time.

Trojan horse

“Our study demonstrated that nanocircles can act like a Trojan horse,” Kool said. “They enter cells and start producing ribozymes that can be targeted against a particular gene. But the nanocircle itself does not replicate itself and eventually leaves the cell.”

Kool’s goal is to create nanocircles that can inhibit disease-causing and mutant genes in people that could be used to treat a variety of illnesses from AIDS to cancer. As a first step, his lab is developing nanocircles that will shut down genes in tiny worms called nematodes.

“We also would like to see if we can use nanocircles to eliminate a harmful bacterium or virus by shutting down an essential gene inside the organism itself – a true Trojan horse,” Kool added.

He also noted that nanocircle technology could prove less expensive than making ribozymes directly and adding them to cells – because relatively small numbers of nanocircles can produce thousands of ribozymes.

The PNAS study was funded by the U.S. Department of Defense Breast Cancer Research Program, administered by the U.S. Army.


Story Source:

The above story is based on materials provided by Stanford University. Note: Materials may be edited for content and length.


Cite This Page:

Stanford University. ""Nanocircles" Act As Trojan Horse To Shut Down Disease-Causing Genes, Study Finds." ScienceDaily. ScienceDaily, 25 January 2002. <www.sciencedaily.com/releases/2002/01/020125073841.htm>.
Stanford University. (2002, January 25). "Nanocircles" Act As Trojan Horse To Shut Down Disease-Causing Genes, Study Finds. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2002/01/020125073841.htm
Stanford University. ""Nanocircles" Act As Trojan Horse To Shut Down Disease-Causing Genes, Study Finds." ScienceDaily. www.sciencedaily.com/releases/2002/01/020125073841.htm (accessed July 23, 2014).

Share This




More Health & Medicine News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Stone Fruit Listeria Scare Causes Sweeping Recall

Stone Fruit Listeria Scare Causes Sweeping Recall

Newsy (July 22, 2014) — The Wawona Packing Company has issued a voluntary recall on the stone fruit it distributes due to a possible Listeria outbreak. Video provided by Newsy
Powered by NewsLook.com
Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Huge Schizophrenia Study Finds Dozens Of New Genetic Causes

Newsy (July 22, 2014) — The 83 new genetic markers could open dozens of new avenues for schizophrenia treatment research. Video provided by Newsy
Powered by NewsLook.com
CDC Head Concerned About a Post-Antibiotic Era

CDC Head Concerned About a Post-Antibiotic Era

AP (July 22, 2014) — Sounding alarms about the growing threat of antibiotic resistance, CDC Director Tom Frieden warned Tuesday if the global community does not confront the problem soon, the world will be living in a devastating post-antibiotic era. (July 22) Video provided by AP
Powered by NewsLook.com
Courts Conflicted Over Healthcare Law

Courts Conflicted Over Healthcare Law

AP (July 22, 2014) — Two federal appeals courts issued conflicting rulings Tuesday on the legality of the federally-run healthcare exchange that operates in 36 states. (July 22) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins