In other words, is the mRNA damaged or somehow "marked completed" in the translation process? Or does it pop out the other side of a ribosome ready to be translated again? If the latter, how many copies of a protein result from a single strand of mRNA?

Thank you in advance!

  • 3
    $\begingroup$ A relevant question, but the topic is covered in general textbooks in the section on translation. On the web try searching for polysomes and then think about what their existence implies. A search for mRNA half-life will reveal the answer: “It depends on the mRNA and the organism.” $\endgroup$
    – David
    May 5 at 15:43
  • $\begingroup$ Thank you for the pointer, @David. With your assistance, I think I was able to answer the question. $\endgroup$
    – Brian Rak
    May 6 at 15:15

I'm answering my own question for the benefit of anyone else who might be wondering about this. (Please note that I'm just a programmer, not a biologist, but thanks to David's comment, I was able to come to what I think are some correct conclusions.)

A single mRNA strand can be translated more than once, even more than once at the same time. The polysome that David references is a group of two or more ribosomes all attached to the same mRNA strand, all working on translating it simultaneously.

I believe that it may be possible for a single mRNA strand to be translated hundreds or even thousands of times. My reasoning for this is that a virus injects one copy of its RNA into a cell, and from this one copy, new viruses are replicated until the cell bursts. This "burst size" varies by host cell and virus, but it can range from hundreds to tens of thousands or more. While there are still a lot of things I don't understand about the specific steps the RNA goes through (are there intermediary copies made from which multiple mRNA strands are produced?, etc.), it still seems to suggest that a single strand of mRNA can be translated a lot.

  • $\begingroup$ Note that for translation and transcription are two different things. Transcription is copying the RNA into new RNA. Translation "reads" the RNA and makes protein. Your third paragraph confuses the two. In the case of SARS-CoV-2, the RNA genome (+ sense single stranded (+ss) for this virus) is the same as a mRNA in a cell, but it is copied into a double stranded RNA and then made into a new +ss for packaging and translation. see here $\endgroup$
    – bob1
    May 6 at 20:44
  • $\begingroup$ Thanks for the comment, @bob1. What I meant by that remark was that I didn't know if the viral RNA was the actual thing being translated or not. Conceivably (at least to my naive mind), the "master" RNA could first be transcribed into intermediary copies which are then translated. I reasoned that this might allow thousands of copies of a virus to be replicated even though a single mRNA strand can only be translated a smaller number of times. I was trying to acknowledge the holes in my knowledge that would invalidate my earlier, simpler logic. $\endgroup$
    – Brian Rak
    May 6 at 22:53
  • $\begingroup$ See the diagram in the paper that I linked. It shows that the incoming COV-2 is partially translated to produce a replication and transcription protein which forms a complex with the RNA, which then produces dsRNA and goes on to produce ssRNA for both translation and viral progeny. $\endgroup$
    – bob1
    May 6 at 23:28
  • $\begingroup$ @bob1, Wow, there is a lot to unpack there. Thank you for the help and pointers! $\endgroup$
    – Brian Rak
    May 7 at 15:54
  • $\begingroup$ The question asks about mRNA, but your answer seems focused on one particular viral RNA. It fails to address the differences in mRNA half-lives between species (eukaryotes v. prokaryotes) and within species. Nor does it address the mechanism of mRNA degradation. I suggest you need to do more reading if you really wish to understand the answer to the question you have asked. Have you searched this site to see if the topic has been covered previously? $\endgroup$
    – David
    May 7 at 19:20

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