We have completed maintenance on DiscoverMagazine.com and action may be required on your account. Learn More

Four-Stranded DNA Makes Human Debut

Contrary to biological dogma, it appears human DNA can sometimes form a quadruple helix.

By Breanna Draxler
Jan 27, 2014 12:00 AMOct 25, 2019 3:48 PM
Four-Stranded DNA Makes Human Debut
This top view of a G-quadruplex shows its structure in the DNA of a human telomere, where they frequently form. Thomas Splettstoesser/Wikimedia Commons


Sign up for our email newsletter for the latest science news

In describing the two-stranded structure of DNA, Cambridge University biologists James Watson and Francis Crick gave us the image of a twisting ladder they called a double helix. The rungs were connected by pairs of chemical bases called nucleotides: Adenine (A) paired with thymine (T), and cytosine (C) with guanine (G). 

Now, 60 years later, researchers from the same institution have found a quadruplehelix — previously described only in microorganisms — in human cells. In place of rungs, the twisting, four-sided tower has platforms with a guanine nucleotide on each of four corners, hence the name G-quadruplex.

Chemist Shankar Balasubramanian and colleagues found the structures by engineering a special, fluorescent antibody that binds specifically to the four-stranded form. Initial results, published in January, trace the structures to cellular regions associated with explosive growth: telomeres, the protective caps of chromosomes implicated in aging and longevity, and cancer-causing genes. 

G-quadruplexes may be linked to cancer, speculates molecular biologist David Tannahill, a member of the Cambridge team. If his suspicion bears out, then deploying these antibodies, which halt the replication of the quads, could present a means of treating malignant tumors. 

What’s a G-Quadruplex?

The G-quadruplex is like a three-dimensional tower with multiple floors. Each floor, called a tetrad, has a guanine (G) base on all four corners. These G’s are held together with hydrogen bonds. A single strand of DNA can fold onto itself to form a G-quadruplex, or guanines from multiple strands can bond to form the four-stranded structure.

The antibody used in the study, called BG4, binds with quadruple helices and glows red. The glowing structures are visible here in the nucleus of a human bone cancer cell (left) and on the telomeres at the ends of chromosomes in cervical cancer cells (right). Jean-Paul Rodriguez and Giulia Biffi/Cancer Research UK Cambridge Institute

[This article originally appeared in print as "Four-Stranded DNA Makes Human Debut."] 

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 40% off the cover price when you subscribe to Discover magazine.

Copyright © 2024 Kalmbach Media Co.