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
MAY 16, 2020
Neuroscience
Stem Cell Method (Parkinson's) Could Avoid Transplant Rejection
MAY 16, 2020
Stem Cell Method (Parkinson's) Could Avoid Transplant Rejection
Researchers at McLean Hospital and Massachusetts General Hospital (MGH) have tested a stem cell treatment method that av ...
JUN 08, 2020
Genetics & Genomics
Infant Study Suggests Musical Ability is Innate
JUN 08, 2020
Infant Study Suggests Musical Ability is Innate
There are plenty of musical families, and research has suggested that musical abilities have a genetic component.
JUN 10, 2020
Genetics & Genomics
Our Genes Influence How Sensitive We Are
JUN 10, 2020
Our Genes Influence How Sensitive We Are
Maybe you've been told that you are too sensitive, or you know someone who has strong reactions to positive, negative, o ...
JUL 05, 2020
Plants & Animals
A New Way to Estimate a Dog's Age
JUL 05, 2020
A New Way to Estimate a Dog's Age
People have long thought that a dog's age can be estimated by substituting one human year with seven dog years.
JUL 14, 2020
Genetics & Genomics
The Human X Chromosome is Sequenced From End to End
JUL 14, 2020
The Human X Chromosome is Sequenced From End to End
In a major milestone, scientists have completed the first sequence of a human chromosome that reaches from one end to th ...
JUL 30, 2020
Genetics & Genomics
How Are DNA Testing Companies Helping the Fight Against COVID?
JUL 30, 2020
How Are DNA Testing Companies Helping the Fight Against COVID?
One of the most puzzling characteristics of coronavirus is how some people develop severe symptoms and die from the dise ...
Loading Comments...