By synthesizing enzymes using artificial genetic material that does not exist in nature, scientists show DNA and RNA may not be the only ways to kick-start life.
Previously, it was thought that the presence of RNA and DNA was necessary to speed up or catalyze the chemical reactions that kick-start life.
Now, in the journal Nature, a team of Medical Research Council (MRC) scientists explains how they used XNA - artificial genetic material they made in the lab - to make enzymes that do not occur in nature but behave like the ones essential to life.
The achievement will help scientists find out more about the origins of life and could lead to a new generation of drugs and completely new ways of investigating and diagnosing diseases.
Dr. Philipp Holliger, who led the study at the MRC Laboratory of Molecular Biology in Cambridge, UK, says:
"All life on earth depends on a series of chemical reactions, from digesting food to making DNA in our cells. Many of these reactions are too sluggish to happen at ambient temperatures and pressures, and require enzymes to kick-start or 'catalyse' the process."
Life's choices may not be limited to RNA and DNA
Dr. Holliger explains that until recently, scientists believed DNA and RNA were the only molecules capable of storing genetic information. Also, it was thought that only DNA and RNA - together with proteins - could form enzymes. But now, he says:
"Our work suggests that, in principle, there are a number of possible alternatives to nature's molecules that will support the catalytic processes required for life. Life's 'choice' of RNA and DNA may just be an accident of prehistoric chemistry."
The new study builds on previous work done at the MRC lab, where Dr. Holliger and his team made XNAs - synthetic molecules that can store and pass on genetic information in a similar way to DNA.
However, to fully mimic what happens in nature, the building block XNAs have to be able to self-replicate. This is where enzymes come in, because they carry out the cutting and pasting that goes on during self-replication.
Artificial enzymes that can cut and paste RNA
In their new study, the team describes how they got their XNAs to make "XNAzymes" and showed they can cut and paste small chunks of RNA, in the same way as natural enzymes. One of the XNAzymes can even join strands of XNA together - a key step to creating a living system.
The finding raises the possibility that living systems can emerge from molecules different to those that led to life on Earth: "it widens the possible number of planets that might be able to host life," says first author Dr. Alex Taylor, a researcher in the MRC lab and also of St. John's College, Cambridge.
Because they are more stable than natural enzymes, the team hopes their XNAzymes will be useful for making new drugs to tackle diseases that take hold by disrupting cell functions - such as cancer and viral infections.
"Our XNAs are chemically extremely robust and, because they do not occur in nature, they are not recognized by the body's natural degrading enzymes. This might make them an attractive candidate for long-lasting treatments that can disrupt disease-related RNAs," says Dr. Holliger.
Funding for the study came from the MRC, European Science Foundation and the Biotechnology and Biological Sciences Research Council.
Exactly how genetic material is replicated in nature is somewhat of a mystery to scientists. But recently, Medical News Today learned of a new genetic replication study led by Florida State University that offers new insights into this poorly understood area. The team hopes their findings will lead to new cancer treatments.