DNA is made up of a gene alphabet of 4 letters. These letters combine to encode directions for the proteins (that perform most of the key jobs inside cells) to know what to do. A group of scientists have spent the last couple decades engineering a new DNA that includes 2 more man-made letters. They believe that by expanding the genetic alphabet to 6 letters it could give an organism the ability to produce new proteins never seen before in nature. Within this radical discovery lies the potential for new drugs which could someday be the cure for cancer and much more.
It is known that DNA is the blueprint for all life forms on Earth. It is written in a code consisting of four “letters”: A, T, C and G, which pair up in the DNA double helix. This code is the instructions manual for life to grow, develop, survive, and reproduce. It does this with proteins. Proteins are limited to only 20 building blocks, known as amino acids.
“Proteins have become an important new type of drug, because cells can do the work of making them and because molecular biology techniques can be used to help proteins “evolve” to have desired properties,” study leader Floyd Romesberg, a chemical biologist at The Scripps Research Institute in La Jolla, California, said.
The ultimate goal is to create “designer” organisms that can produce artificial proteins, which could be used to produce better drugs. These artificial proteins made from a 6 letter genetic code would, theoretically, produce new amino acids resulting in countless more possibilities. It would mean there would be more than only 20 building blocks.
Romesberg explained in his speech on TED Talks: “Such an organism would be the first radically altered form of life ever created. It would be a semisynthetic form of life that stores more information than life ever has before. It would be able to make new proteins, proteins built from more than the 20 normal amino acids that are usually used to build proteins.”
To begin with, he and his team modified cells of Escherichia coli bacteria by inserting an additional two letters (synthetic base pair) into its DNA. Their single-celled organism was able to hold on indefinitely to the synthetic base pair as it divides. This achievement demonstrated an organism can incorporate artificial DNA letters into its genome. “What we have done is successfully store increased information in the DNA of a living cell,” he told Live Science.
With the power of synthetic chemistry and molecular biology and just under 20 years of work, they created bacteria with six-letter DNA. Just recently, they were able to get them to produce protein using the new letters. They envision these semisynthetic cells to act as little factories to produce better protein. The team from the US, China and France have published their work in PNAS journal.
A few examples of what could be possible with these new semisynthetic organisms include:
- Proteins that use new amino acids with things attached to them that protect them from their environment, that protect them from being degraded or eliminated resulting in a better drug. (One of the problems some drugs face today are they are rapidly degraded or eliminated upon entering the body.)
- An injection of semisynthetic organisms that seek out cancer cells and only when they find them, secrete a toxic protein that kills.
- Oil-eating bacteria to clean up oil spills.
The best part is, these organisms need to be fed the chemical precursors, the 2 synthetic letters which are completely different from anything that exists in nature, in order to survive. Natural cells neither have them nor have the ability to make them. Therefore, if deployed into a person or out into nature where they no longer have access to that special food, they can grow and survive for a little while, just long enough to perform their intended function. Eventually, they starve to death and just disappear.
“Maybe life as we know it isn’t the only way it could be. Maybe we’re not the only solution, maybe not even the best solution, just a solution.” This study suggests that all of life’s processes can be subject to manipulation. These cells are a new form of life. They are living and growing and making protein with a six-letter alphabet. The world now has a semisynthetic form of life.