APR 24, 2018 6:51 AM PDT

Found in Live Cells: A New Form of DNA

WRITTEN BY: Carmen Leitch

When most people think about DNA, they think of the familiar double helix shape. But now researchers have identified a different kind of structure in DNA, one called the i-motif that is a kind of knot. This marks the first time it's ever been seen in live cells. The findings have been reported in Nature Chemistry by scientists at the Garvan Institute of Medical Research.

This is an artist's impression of the i-motif DNA structure inside cells, along with the antibody-based tool used to detect it.  / Credit: Chris Hammang

It has been known that DNA can take on physical shapes other than the double helix, but that had only been observed in the laboratory. Researchers have suggested that these structural differences might impact how genes are read by cellular machinery.

"When most of us think of DNA, we think of the double helix," said the co-leader of the research, Associate Professor Daniel Christ, Head of the Antibody Therapeutics Lab at Garvan. "This new research reminds us that totally different DNA structures exist - and could well be important for our cells."

There are four nucleotide bases that make up DNA: A, T, C and G. "The i-motif is a four-stranded 'knot' of DNA,” added study co-leader Associate Professor Marcel Dinger, Head of the Kinghorn Centre for Clinical Genomics at Garvan. "In the knot structure, C letters on the same strand of DNA bind to each other - so this is very different from a double helix, where 'letters' on opposite strands recognize each other, and where Cs bind to Gs."

These findings should resolve a debate about whether the i-motif was something only produced in the lab, which never appears under natural conditions. They used a special tool to find the i-motif, a very specific antibody. That molecule binds to i-motifs in a very specific way, like a key is made for a lock. 

That antibody, which has been elusive and was critical for this work, does not attach to DNA when it is in a helical form. It also doesn’t recognize another form of DNA,  G-quadruplex structures. The investigators found the i-motif DNA in a variety of human cell lines and used fluorescence to pinpoint its locations (in green). 

"What excited us most is that we could see the green spots - the i-motifs - appearing and disappearing over time, so we know that they are forming, dissolving and forming again," said Dr. Mahdi Zeraati, whose work laid a foundation for this study.

The team also determined that during a particular point in the cell’s life, or what is known as the cell cycle, the i-motif appears - the late G1 phase. At that time, i-motifs show up in areas of DNA that control gene expression. They were also present at the caps on the ends of chromosomes, telomeres.

"We think the coming and going of the i-motifs is a clue to what they do,” said Zeraati. “It seems likely that they are there to help switch genes on or off, and to affect whether a gene is actively read or not."

"We also think the transient nature of the i-motifs explains why they have been so very difficult to track down in cells until now," added Christ.

"It's exciting to uncover a whole new form of DNA in cells - and these findings will set the stage for a whole new push to understand what this new DNA shape is really for, and whether it will impact on health and disease,” concluded Dinger. 


Sources: AAAS/Eurekalert! Via Garvan Institute of Medical Research, Nature Chemistry

About the Author
  • Experienced research scientist and technical expert with authorships on 28 peer-reviewed publications, traveler to over 60 countries, published photographer and internationally-exhibited painter, volunteer trained in disaster-response, CPR and DV counseling.
You May Also Like
JAN 20, 2020
Genetics & Genomics
JAN 20, 2020
Braveheart RNA Structure is Revealed For the First Time
Protein-coding genes only make up a small part of the genome. Much of the rest may contain long, non-coding RNA sequences....
FEB 13, 2020
Genetics & Genomics
FEB 13, 2020
A Very Unusual Virus is Discovered in Brazil
Researchers in Brazil have discovered a very unusual virus infecting amoeba in an artificial lake called Lake Pampulha in the city of Belo Horizonte....
MAR 24, 2020
Clinical & Molecular DX
MAR 24, 2020
Ultra sensitive cancer diagnostic detects DNA "fingerprints" in liquid biopsies
  Researchers from the Broad and Dana-Farber Cancer Institutes have developed a diagnostic technology that can monitor for the presence of recurring c...
MAR 04, 2020
Neuroscience
MAR 04, 2020
Memories Are Stored As Specific Neural Firing Patterns
Scientists working on the EPFL Blue Brain Project explain the algebraic patterns of neuron activity.  Scientists at the National Institute of Health&r...
MAR 30, 2020
Microbiology
MAR 30, 2020
The Microbial Communities That Form on the Tongue
Scientists used a fluorescent imaging tool to analyze how bacteria grow on the human tongue....
APR 01, 2020
Microbiology
APR 01, 2020
How Two Types of Tests for COVID-19 Work
There are a couple of different kinds of tests that researchers will be developing and clinicians will be using to disrupt the COVID-19 pandemic....
Loading Comments...