Featured Research

from universities, journals, and other organizations

Head-on collisions between DNA-code reading machineries accelerate gene evolution

Date:
March 29, 2013
Source:
University of Washington
Summary:
The bacteria Bacillus subtilis places some of their genes in prime collision paths for the moving molecular machineries that read the DNA code. This spatial-organization tactic to evolve and adapt might be imitated in harmful Gram-positive bacteria to strengthen their virulence.

Houra Merrikh, assistant professor of microbiology, and her student Samuel Million-Weaver, University of Washington, study mechanisms that bacteria use to evolve and adapt.
Credit: Christopher Merrikh

Bacteria appear to speed up their evolution by positioning specific genes along the route of expected traffic jams in DNA encoding. Certain genes are in prime collision paths for the moving molecular machineries that read the DNA code, as University of Washington scientists explain in this week's edition of Nature.

The spatial-organization tactics their model organism, Bacillus subtilis, takes to evolve and adapt might be imitated in other related Gram-positive bacteria, including harmful, ever-changing germs like staph, strep, and listeria, to strengthen their virulence or cause persistent infections. The researchers think that these mechanisms for accelerating evolution may be found in other living creatures as well.

Replication -- the duplicating of the genetic code to create a new set of genes- and transcription -- the copying of DNA code to produce a protein -- are not separated by time or space in bacteria. Therefore, clashes between these machineries are inevitable. Replication traveling rapidly along a DNA strand can be stalled by a head-on encounter or same-direction brush with slower-moving transcription.

The senior authors of the study, Houra Merrikh, UW assistant professor of microbiology, and Evgeni Sokurenko, UW professor of microbiology, and their research teams are collaborating to understand the evolutionary consequences of these conflicts. The major focus of Merrikh and her research team is on understanding mechanistic and physiological aspects of conflicts in living cells -- including why and how these collisions lead to mutations.

Impediments to replication, they noted, can cause instability within the genome, such as chromosome deletions or rearrangements, or incomplete separation of genetic material during cell division. When dangerous collisions take place, bacteria sometimes employ methods to repair, and then restart, the paused DNA replication, Merrikh discovered in her earlier work at the Massachusetts Institute of Technology.

To avoid unwanted encounters, bacteria orient most of their genes along what is called the leading strand of DNA, rather than the lagging. The terms refer to the direction the encoding activities travel on different forks of the unwinding DNA. Head-on collisions between replication and transcription happen on the lagging strand.

Despite the heightened risk of gene-altering clashes, the study bacteria B. subtilis still orients 25 percent of all its genes, and 6 percent of its essential genes, on the lagging strand.

The scientist observed that genes under the greatest natural selection pressure for amino-acid mutations, a sign of their adaptive significance, were on the lagging strand. Amino acids are the building blocks for proteins. Based on their analysis of mutations on the leading and the lagging strands, the researchers found that the rate of accumulation of mutations was faster in the genes oriented to be subject to head-on replication-transcription conflicts, in contrast to co-directional conflicts.

According to the researchers, together the mutational analyses of the genomes and the experimental findings indicate that head-on conflicts were more likely than same-direction conflicts to cause mutations. They also found that longer genes provided more opportunities for replication-transcription conflicts to occur. Lengthy genes were more prone to mutate.

The researchers noted that head-on replication-transcription encounters, and the subsequent mutations, could significantly increase structural variations in the proteins coded by the affected genes. Some of these chance variations might give the bacteria new options for adapting to changes or stresses in their environment. Like savvy investors, the bacteria appear to protect most of their genetic assets, but offer a few up to the high-roll stakes of mutation.

The researchers pointed out, "A simple switch in gene orientation …could facilitate evolution in specific genes in a targeted way. Investigating the main targets of conflict-mediated formation of mutations is likely to show far-reaching insights into adaptation and evolution of organisms."


Story Source:

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


Journal Reference:

  1. Sandip Paul, Samuel Million-Weaver, Sujay Chattopadhyay, Evgeni Sokurenko, Houra Merrikh. Accelerated gene evolution through replication–transcription conflicts. Nature, 2013; 495 (7442): 512 DOI: 10.1038/nature11989

Cite This Page:

University of Washington. "Head-on collisions between DNA-code reading machineries accelerate gene evolution." ScienceDaily. ScienceDaily, 29 March 2013. <www.sciencedaily.com/releases/2013/03/130329125307.htm>.
University of Washington. (2013, March 29). Head-on collisions between DNA-code reading machineries accelerate gene evolution. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2013/03/130329125307.htm
University of Washington. "Head-on collisions between DNA-code reading machineries accelerate gene evolution." ScienceDaily. www.sciencedaily.com/releases/2013/03/130329125307.htm (accessed September 18, 2014).

Share This



More Plants & Animals News

Thursday, September 18, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) 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