In the first post of this double we’ve already established that scientist sometimes manage to surprise even themselves with how far they can push the boundaries of science and technology. As if creating nano sized drug-delivery machines and computer chips based on bent at will DNA structures wasn’t enough, we decided to push even further.
DNA is well known for being one of the most stable biopolymers. It is not by chance that our genome is coded in DNA and not something else – if you want vital codes for the operating software of every living creature to be stored and carried over safely, you better chose the hardware wisely! The half-life of a DNA molecule has been calculated to be 521 years! 521 years to destroy a fine, but nonetheless relatively simple molecule built up of 1 type of sugar and 4 nucleic bases, on repeat. And that half-life is calculated for “normal” conditions without the reparatory systems of a living organism to keep it in check. Every organism has a fascinating set of DNA repairing enzymes which continuously counteract the damage inflicted on DNA by the environment (mostly radiation and chemicals) and pathogens. These mechanisms vary greatly between organisms of different complexity, but they are generally based on the ability of an enzyme to recognize a DNA strand (whether or not they recognize its sequence) and stitch back together broken pieces, or insert new ones between breaks of DNA. In addition to this, every cell has molecular machinery, which is responsible for the precise copying of its own DNA for the sake of reproduction – during cellular division (in one way or another – the basis of every life form) the genome of the cell needs to be copied as correctly as possible and divided meticulously between the two new cells. There are tens to hundreds of enzymes involved in this, just to make sure that the new cell is the expected copy of its mother cell. The bottom line is that there is a huge number of enzymes whose only job is to recognize in one way or another DNA and operate it in the living cell.
But what if I told you, that we now have enzymes, which can copy, stitch, multiply, and manage polymers of alien nature? In the era of synthetic biology, we managed to create polymers with properties extremely similar to our own DNA, but based on different sugars and nucelobases than the DNA, giving it unexpected and immensely improved properties. I present you the XNAs (Xeno nucleic acid, or in other words – the alien nucleic acid). By 2011 at least six alternatives of DNA that were believed to be able to store and retrieve information were presented from labs around the world. Our normal DNA operating enzymes though, were not able to recognize those XNAs, so the scientists dived into engineering compatible enzymes via a process called directed evolution, and they were able to not only recognize, but operate at full capacity XNAs.
So by today, we’ve practically proven that DNA and RNA are the molecules that store our genetic make up probably by accident in the history of life, but also that we are able to create much more stable alternatives of the basic genetic machinery – namely the XNAs and XNAzymes. How are they better? To name the major ones – they are much less susceptible to chemical damage, and they are completely unrecognizable by the naturally occurring DNA-handling enzymes, so they are not targeted by them. Simply with those two properties, XNAs can quickly become the researcher’s favorite tool in fighting DNA/RNA related diseases.
On the other hand, XNAs can prove to be the ultimate biosafety tool for genetic engineering for human benefit. Genetically engineering bacteria, plants or even animals with XNAs instead of DNA, and supplying them with the required set of XNAzymes to handle this parts of the genome, researchers can finally put to rest all the fears of “stray genes” escaping a modified organism and suddenly appearing in a wild genome. This way many of humanity’s current needs of medication, vaccines, food and feed can be finally met!
From the toy of the scientists, through the ultimate personalized medicine, to the best yet biosafety measure, XNAs are here to stay and evolve. Whether we ourselves will turn into DNA-XNA hybrids in the foreseeable future is too early to say, but keep an eye on those genetics labs, because they will not seize to surprise you!