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An illustration provided by NCSU shows the critical decoding structure produced when modified nucleosides enable tRNA to decode by “wobble” recognition. Only the decoding region of a 50,000+ atom structure of the ribosome (small subunit) is shown. The modified nucleoside platform (orange) that stabilizes the codon-anticodon interaction, and the modified nucleoside that wobbles (green) are shown. The structure was determined at the atomic resolution of -3 angstroms (3 X 10 –10 meters).
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‘The interest in the scientific community has changed to how and when genes are turned on and off, and pertinent to my research, how the codes in DNA are translated into working proteins. We are interested in the speed and accuracy of how the DNA codes for amino acids are read into the production of proteins.’ – Dr. Paul AgrisUnraveling the secrets of DNA has been a great detective story for decades, with giants of science such as the late Francis Crick and his partner James Watson. Recently, a North Carolina State University professor and other researchers deciphered a few more clues.

Unfortunately, Crick died before one of the theories he expounded took a further step toward being proved true by NCSU’s Paul Agris, a PhD and a professor in the Department of Structural Biochemistry.

It’s called the Wobble Hypothesis.

Asked if the world owes a great deal to Crick and Watson, who were awarded a Nobel Prize for their discovery of DNA, Agris replied: “Absolutely. I have met both. I have a letter from Crick supporting the Modified Wobble Hypothesis. Sorry to have seen him pass- away this year, prior to the publication of the paper.”

Agris and researchers in Great Britain and Poland published the modified wobble theory in the December edition of Nature Structural and Molecular Biology. Crick created the original wobble concept in 1966 in an attempt to explain how DNA codes were translated by RNA even though there are far fewer RNA.

Beyond genome mapping

Mapping the human genome, as great an achievement as it has been, is far from the end to genetic research. Understanding how genomic mapping takes place is crucial to further understanding how DNA/RNA interact and then using that knowledge for drug development or other applications.

“The interest in the scientific community has changed to how and when genes are turned on and off, and pertinent to my research, how the codes in DNA are translated into working proteins,” Agris explained. “We are interested in the speed and accuracy of how the DNA codes for amino acids are read into the production of proteins.

“There are two major areas of interest. We speak of genetic information as if it is individual genes that are turned on or off. Actually there are some 30,000 human genes, many of which are on all the time and some of which are turned on depending on cellular requirements.

“But what is really fascinating – and for which we need more information – is that certain genes are regulated together. Which genes are turned on together, which genes are turned on while others are turned off, which genes are turned off together? Why? What are the advantages for the cell to do so?

“The other major area of interest is how to alter gene expression to the benefit of human health. The work we have accomplished opens some avenues of investigation on how to use RNA chemistry to alter gene expression.”

Understanding the Wobble Hypothesis

So, Local Tech Wire asked, what is the significance of the modified Wobble Hypothesis?

“The Wobble Hypothesis of 1966 was just that an hypothesis,” Agris said. “In 1991, I altered it to the Modified Wobble Hypothesis. Now the original and the modified versions have been proven. Not only proven, but because of the technology (high resolution x-ray crystallography) used to study the way in which the codes are read, we have a physical and chemical understanding of how “wobble” works.

“The Hypothesis was precipitated by the fact that there were too few transfer RNAs (about 40 tRNAs) to read 61 genetic codes for amino acids. tRNAs carry individual amino acids to the protein synthesizing machinery (the ribosome). Each tRNA is specific for a certain amino acid. Each tRNA reads at the ribosome a genetic code for the that specific amino acid. Crick suggested that a single tRNA would have to read more than one code since we have 40 tRNAs and 61 codes. (Mitochondria have even fewer tRNAs.)

“Thus, he coined the use of the word ‘wobble’ as a description of a tRNA reading more than one code.

“In studying tRNA biochemistry, I found that cell’s have to chemically alter the area of some tRNA molecules that reads the genetic codes for the tRNA to be accurate and specific in that reading. Thus, I proposed a Modified Wobble Hypothesis that says that chemical modifications of tRNA in some case restrict code reading to one or two codes, whereas other modifications expand code reading to three or even four codes.”

Argis, who earned B.S. degrees in chemistry and biology at Bucknell University in 1966 and his PhD at the Massachusetts Institute of Technology in 1971, said the Wobble Hypothesis captured his attention “when I discovered that the cell’s chemical modifications were important for tRNAs to be able to read the genetic codes.”

Argis’ work could prove crucial to the development of drugs and “new ways to target the protein synthesis machinery in pathogens” as scientists better understand the tRNA codes.

“The chemical modifications important to the Modified Wobble Hypothesis can be used as targets of new antibiotics,” Argis said. “They also can be used as tools in the creation of new proteins, possibly with new amino acids.”

Argis also pointed out that NCSU owns a patent on a “cell’s particular chemical modifications in translation.”

A key to understanding how all DNA translation works is the process called x-ray crystallography which provided atom-level information.

“X-ray crystallography produces a snap-shot of the time at which the tRNA is physically decoding the genomic information,” Argis explained. “We turn the x-ray information into a 3D picture of the chemical interaction that has taken place.”

For more details on Argis’ work, see: biochem.ncsu.edu/faculty/agris/agris.htm