Tardigrades, also known as water bears, are hailed as the hardiest animal on Earth. The eight-legged aquatic animals can survive boiling and freezing temperatures and even seemingly deadly levels of radiation.

Earlier this year, Japanese researchers were even able to bring back to life tardigrades that have been frozen for 30 years. How do these animals survive extreme conditions?

Scientists earlier believed that the animals survive exposure to radiation by repairing the damage done to their DNA. In a study conducted over a period of eight years, Takekazu Kunieda, from the University of Tokyo, and colleagues were able to identify what is behind the tardigrades' remarkable resilience.

Findings of a new study published in the journal Nature Communications on Sept. 20 revealed that the secret to the animal's superpowers lies on a protein-coated DNA.

Kunieda and colleagues sequenced the entire genome of the tardigrade species Ramazzottius varieornatus and found the strange protective protein called Dsup, which is short for "damage suppressor," that appears to protect the tardigrades' DNA from radiation damage.

When the researchers engineered human cells to generate the Dsup protein, they noticed that the cells experienced significantly less damage from radiation compared to unprotected cells when these were irradiated.

The researchers found that the human cells that were shielded by the protein experienced 40 percent less X-ray damage.

"Using human cultured cells, we demonstrate that a tardigrade-unique DNA-associating protein suppresses X-ray-induced DNA damage by ∼40% and improves radiotolerance," the researchers wrote in their study.

The researchers theorize that the protein gently wraps itself around the tardigrade DNA, which protects the animal from harm without causing interruptions to its function.

"We guess that Dsup binds densely to DNA to provide a shield against environmental stress, somehow making DNA inaccessible to any damaging agents," Kunieda said. "To our knowledge, this is the first identification of a DNA-associating protein which confers DNA protection and improved tolerance to radioactivity in animal cells."

Researchers said the findings have important implications. Genes like Dsup may be used to make the storage and transportation of human cells safer and easier. These genes may help protect delicate human skin grafts from getting damaged. Such genes may also help scientists bioengineer organisms so they can survive in extremely hostile environments such as on the surface of planet Mars.

"These findings indicate the relevance of tardigrade-unique proteins to tolerability and tardigrades could be a bountiful source of new protection genes and mechanisms," the researchers said.

Photo: Goldstein lab | Flickr 

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