Featured Research

from universities, journals, and other organizations

Researchers identify seventh and eighth bases of DNA

Date:
July 21, 2011
Source:
University of North Carolina School of Medicine
Summary:
For decades, scientists have known that DNA consists of four basic units -- adenine, guanine, thymine and cytosine. Those four bases have been taught in science textbooks and have formed the basis of the growing knowledge regarding how genes code for life. Yet in recent history, scientists have expanded that list from four to six. Now, researchers have discovered the seventh and eighth bases of DNA.

The newly discovered seventh and eighth bases of DNA -- called 5-formylcytosine and 5 carboxylcytosine -- are actually versions of cytosine that have been modified by Tet proteins, molecular entities thought to play a role in DNA demethylation and stem cell reprogramming.
Credit: Rodolfo Clix / Fotolia

For decades, scientists have known that DNA consists of four basic units -- adenine, guanine, thymine and cytosine. Those four bases have been taught in science textbooks and have formed the basis of the growing knowledge regarding how genes code for life. Yet in recent history, scientists have expanded that list from four to six.

Related Articles


Now, with a finding published online in the July 21, 2011, issue of the journal Science, researchers from the UNC School of Medicine have discovered the seventh and eighth bases of DNA.

These last two bases -- called 5-formylcytosine and 5 carboxylcytosine -- are actually versions of cytosine that have been modified by Tet proteins, molecular entities thought to play a role in DNA demethylation and stem cell reprogramming.

Thus, the discovery could advance stem cell research by giving a glimpse into the DNA changes -- such as the removal of chemical groups through demethylation -- that could reprogram adult cells to make them act like stem cells.

"Before we can grasp the magnitude of this discovery, we have to figure out the function of these new bases," said senior study author Yi Zhang, Ph.D., Kenan Distinguished Professor of biochemistry and biophysics at UNC and an Investigator of the Howard Hughes Medical Institute. "Because these bases represent an intermediate state in the demethylation process, they could be important for cell fate reprogramming and cancer, both of which involve DNA demethylation."

Much is known about the "fifth base," 5-methylcytosine, which arises when a chemical tag or methyl group is tacked onto a cytosine. This methylation is associated with gene silencing, as it causes the DNA's double helix to fold even tighter upon itself.

Last year, Zhang's group reported that Tet proteins can convert 5 methylC (the fifth base) to 5 hydroxymethylC (the sixth base) in the first of a four step reaction leading back to bare-boned cytosine. But try as they might, the researchers could not continue the reaction on to the seventh and eighth bases, called 5 formylC and 5 carboxyC.

The problem, they eventually found, was not that Tet wasn't taking that second and third step, it was that their experimental assay wasn't sensitive enough to detect it. Once they realized the limitations of the assay, they redesigned it and were in fact able to detect the two newest bases of DNA. The researchers then examined embryonic stem cells as well as mouse organs and found that both bases can be detected in genomic DNA.

The finding could have important implications for stem cell research, as it could provide researchers with new tools to erase previous methylation patterns to reprogram adult cells.

It could also inform cancer research, as it could give scientists the opportunity to reactivate tumor suppressor genes that had been silenced by DNA methylation.

The research was funded by the Howard Hughes Medical Institute and the National Institutes of Health.

Study co-authors from UNC include Shinsuke Ito, Ph.D.; Li Shen, Ph.D.; Susan C. Wu, Ph.D.; Leonard B. Collins and James A. Swenberg, Ph.D.


Story Source:

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


Journal Reference:

  1. Shinsuke Ito, Li Shen, Qing Dai, Susan C. Wu, Leonard B. Collins, James A. Swenberg, Chuan He, Yi Zhang. Tet Proteins Can Convert 5-Methylcytosine to 5-Formylcytosine and 5-Carboxylcytosine. Science, 2011; DOI: 10.1126/science.1210597

Cite This Page:

University of North Carolina School of Medicine. "Researchers identify seventh and eighth bases of DNA." ScienceDaily. ScienceDaily, 21 July 2011. <www.sciencedaily.com/releases/2011/07/110721142408.htm>.
University of North Carolina School of Medicine. (2011, July 21). Researchers identify seventh and eighth bases of DNA. ScienceDaily. Retrieved December 22, 2014 from www.sciencedaily.com/releases/2011/07/110721142408.htm
University of North Carolina School of Medicine. "Researchers identify seventh and eighth bases of DNA." ScienceDaily. www.sciencedaily.com/releases/2011/07/110721142408.htm (accessed December 22, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Monday, December 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Christmas Kissing Good for Health

Christmas Kissing Good for Health

Reuters - Innovations Video Online (Dec. 22, 2014) Scientists in Amsterdam say couples transfer tens of millions of microbes when they kiss, encouraging healthy exposure to bacteria. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Brain-Dwelling Tapeworm Reveals Genetic Secrets

Brain-Dwelling Tapeworm Reveals Genetic Secrets

Reuters - Innovations Video Online (Dec. 22, 2014) Cambridge scientists have unravelled the genetic code of a rare tapeworm that lived inside a patient's brain for at least four year. Researchers hope it will present new opportunities to diagnose and treat this invasive parasite. Matthew Stock reports. Video provided by Reuters
Powered by NewsLook.com
Touch-Free Smart Phone Empowers Mobility-Impaired

Touch-Free Smart Phone Empowers Mobility-Impaired

Reuters - Innovations Video Online (Dec. 21, 2014) A touch-free phone developed in Israel enables the mobility-impaired to operate smart phones with just a movement of the head. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Earthworms Provide Cancer-Fighting Bacteria

Earthworms Provide Cancer-Fighting Bacteria

Reuters - Innovations Video Online (Dec. 21, 2014) Polish scientists isolate bacteria from earthworm intestines which they say may be used in antibiotics and cancer treatments. Suzannah Butcher reports. Video provided by Reuters
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:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

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