Wikipedia:Reference desk/Archives/Science/2020 December 2

= December 2 =

RNA induced protein production life cycle
I thought it was a simple question, but obviously the RNA vaccines articles are still evolving. I was wandering how long after a cell has been programmed to produce a protein with the mRNA, does it do this for? Is it a one off production, or a switch until cell retirement? Lee&there4;V 10:20, 2 December 2020 (UTC)
 * One hopes that they last about as long as regular mRNAs, with a halflife of a few minutes. Abductive  (reasoning) 20:49, 2 December 2020 (UTC)
 * mRNA associates with a ribosome and a protein is translated from it. The process repeats itself until mRNA is damaged or degraded by enzymes. Ruslik_ Zero 20:52, 2 December 2020 (UTC)


 * I have some doubts that the terminology of "reprogramming" the cell, or the cell being "programmed", is correct. Normally, that would be understood to mean that the genetic code is somehow incorporated into the cell's DNA, as in genetic engineering. To elaborate on the earlier responses, the process of protein synthesis, after externally produced (mature) mRNA has been introduced in the cell, is more or less automatic – unlike the regulated process of the transcription of DNA to mRNA. As long as the mRNA is actively being translated, it is protected against degradation, but when inactive it is subject to decay. When degraded, it is unusable for further protein synthesis. So it is not quite one-off, but close. --Lambiam 21:22, 2 December 2020 (UTC)
 * thank you, I was hoping that was the case, but couldn't see the wood for the trees! Lee&there4;V 12:51, 4 December 2020 (UTC)
 * It's also worth noting that the production wouldn't have to last very long for this to be effective. Basically, these mRNA vaccines are coding for the proteins that are the antigens for the immune system to recognize and be "trained" to have immunity against the virus. Traditional vaccines introduce these protein antigens directly, either by making a deactivated virus that still has the required antigens, or by using fragments of destroyed virus with the antigens, or otherwise manufacturing the protein antigens. Protein synthesis is not at all a simple thing, and neither is the development of inactivated viruses, etc. mRNA, on the other hand, is relatively simple to synthesis (relative to proteins, at least), and then our bodies have excellent machinery to translate the mRNA into proteins. In a traditional vaccine, the protein antigens would not last very long in the body, but they do not have to. They only need to last long enough to train things like memory B cells in the immune system, and after the antigen is gone, the body will still recognize it and trigger a successful immune response in the future (that's the scientific basis for vaccines in general). The mRNA only needs to last long enough for enough translation to take place and make the protein antigen, and then the protein antigen only needs to last long enough to trigger an immune response. After that, job is done. --OuroborosCobra (talk) 16:24, 4 December 2020 (UTC)
 * But conventional vaccines deliver their antigens in the extracellular space and blood circulation where they can meet with memory B cells. An injection of mRNA must also deliver most of its mRNA outside cells, where it probably cannot be translated, so it must first enter cells to be translated into proteins. Questions: how does mRNA enter cells in the first place? And how do the translated proteins exit the cells in order to meet with memory B cells? Thanks 2003:F5:6F09:B100:7185:8061:156A:2E5 (talk) 14:06, 5 December 2020 (UTC) Marco PB
 * Did you read RNA vaccines? It covers the different basic approaches quite well. For an effective uptake into cells, you have to "bait" them to take up stuff with the mRNA in it, and at the same time protect the mRNA from degradation, which would normally eliminate all external nucleic acids that enter the cell. And the produced proteins don't really need to exit the cell, because our cells have effective methods to present (almost) all proteins being produced (or better peptide fragments thereof) to the immune system: Major histocompatibility complex. So that's basically what you are trying to accomplish with an mRNA vaccine: piggybacking your vaccine into the body's own "danger monitoring system". TheMaster17 (talk) 11:44, 8 December 2020 (UTC)