The convention of genomic research is to present all RNA sequences as equivalent cDNA sequences. As this will be the output of most common sequencing platforms.
DNA is way more stable than RNA. Since you can easily synthesize RNA from DNA, and DNA synthesis technology is much more mature, folks normally synthesize DNA and then derive/make the RNA from it. That makes most researches default to DNA 5' to 3', even when talking about RNA.
Note that independently of the notation used the mRNA of those vaccines use even more "weird" bases, such as 1-methyl-3’-pseudouridylyl, to make the vaccine mRNA not be detected by the immune system [1].
DNA uses base pairs [A,T] and [G,C], this code is for a piece of DNA,. if you keep a DNA sequence in vials for later use, that is much more stable and easier to manipulate, and repair when corrupted.
normally RNA in vivo is complexed with protiens that prevent RNA from folding, and annealing into structure that is not compatible with translation to protien. In the vaccine this isnt happening, this is why RNA is hard to work with and the vaccine must be kept so cold.
This is not to say that DNA is simple to work with, but it solves problems if you dont need direct access to RNA.
RNA uses uracil/uridine rather than thymine, but uridine is actually quite immunogenic. That's what has prevented people from using mRNA as a therapy until recently, when the founders of BioNTech figured out that they could use pseudouridine (abbreviated as Ψ) instead. See [1] for more information.
Can somebody explain to me why?