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Twisted Knot-Shaped DNA Structure Discovered in Human Living Cells

DNA strand/ Photo By Sergey Nivens via 123RF

 


Researchers at Garvan Institute of Medical Research upped the bar with a breakthrough discovery since the 1953 unveiling of the iconic DNA double helix by Cambridge University scientists James Watson and Francis Crick. The research revealed that DNA shape isn’t always “double-stranded” but also “knot-twisted.”


Recent findings published in the journal Nature Chemistry called the new DNA structure i-motif which looks similar to a “twisted knot” and was seen inside living cells for the very first time.  

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

 

The Double-Helix DNA

DNA or deoxyribonucleic acid is the molecule that contains human genes where information needed to live, grow, and multiply is stored in living cells. All 6 billion A (adenine), C (cytosine), G (guanine) and T (thymine) bases are DNA codes that accurately dictate the genetic blueprint of life. It is shaped like a twisted ladder or “double helix” and is indispensable to our survival.

DNA was actually discovered in 1869, it’s genetic inheritance was determined in 1943 and its structure, the famous double helix, was known in 1953 courtesy of Watson and Crick.

In the book, “Double Helix” published in 1968, Watson explained their findings that DNA replicates itself by separating into individual strands. Each strand became another template to form a new double helix.

Crick announced their discovery in between blurts in a pub that “they have discovered the secret of life.” This claim actually rang scientific bells since they were able to solve humanity’s mystery on how organisms pass on genetic instructions from one generation to the next.

Their findings revolutionized fields of biology and medicine which were seen and felt in the prenatal screening of disease genes, genetically engineered foods, treatment designs for diseases such as AIDS, in forensic science for identification of human remains, and in the assessment of physical evidence in a crime scene investigation.

 

I-Motif Structure


Scientists revealed the presence of green spots called i-motifs that appeared and disappeared during the process of observation. They suspected that these shapes were actually forming, dissolving, and forming again over time. Moreover, they are presumed to play an important role in the “reading” of the DNA code.

"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," said Prof. Christ.

The research was able to identify when the i-motifs appear in a cell’s life cycle. In their observation, i-motifs form at the late phase of the G1 when the DNA is actively “being read.”

 

DNA strand/ Photo By Tatiana Shepeleva via 123RF

 

Dr. Mahdi Zeraati, co-lead of the research, said, "We think the coming and going of the i-motifs is a clue to what they do. 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," he added.

The i-motifs were also seen in the promoter regions of DNA where genes are controlled or switched on or off, as well as in the end sections or “telomeres”  of the chromosomes responsible for the aging process.

The research team was ecstatic over the unveiling of a whole new form of DNA cells. They are looking at this new insight as a precursor of further research to fully understand what the i-motif shape is meant for and its possible impact on diseases and overall health.

 

Identifying the I-Motif


The lab process entailed observation in living cells, a first milestone in the study of DNA. In order to detect, locate, and identify i-motif DNA,  the researchers designed tiny probes that recognized the DNA knots.

The tiny probes were created using fragments of an antibody molecule, the Y-shaped molecule with specific substances. For the benefit of the experiment, the antibody was engineered so that it would recognize and attach itself to i-motifs but not to any other form of DNA.

Researchers used the fluorescence technique (dye) in order to espy the location of the i-motifs in the human cell landscape. The process assisted the researchers to look into numerous green spots within the nucleus. 

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