4 ms·

Can you add any number of A's, or just 1, or shorten it by 1, and it still is functional?

subroutine 4y ago
The number of adenine repeats that confer functional properties is quite variable but it definitely needs to be more than "just 1". I've seen anywhere from 25-250 used in designed plasmids. The exact number people use in their engineered sequence is based on a number of factors, not all of them scientific in nature (e.g. companies charge per basepair synthesize a bespoke polypeptide; e.g. you copied the sequence from a previous clone into ApE and that sequence used 30 repeats and worked fine).
- deleted 4y ago
  [deleted]
- kevviiinn 4y ago
  Iirc there's a protein that adds 12-15 slowly then another protein comes in and adds another 200+ when it detects the start of the tail. Not sure about the details about how or why it stops tho. At least when considering mRNA getting prepped for nuclear export
  - subroutine 4y ago
    You are probably right, I'm not an expert on this process. But there's likely a difference between the innate eukaryotic cell polyadenylation process vs. how coronavirus accomplishes polyadenylation because coronavirus rna never enters the nucleus.
kolinko 4y ago
In this case it probably works most reliably with around this number of As, and less/more would decrease reliability, butnitmwould still be functional. Most of genetics is like that.
- kevviiinn 4y ago
  With more As you risk running into the upper limit on sequence length for the virus shell and with less you run the risk of quicker degradation and not enough expression
  - subroutine 4y ago
    The first point being only a concern if you are a virus. If instead you are engineering say, an rna vaccine, you could package your transcript into lipofectamine instead of a coronavirus envelope ;) but point taken, there's always an upper limit.
    - kevviiinn 4y ago
      Also a concern when engineering viruses for research or other treatments such as the AAVs
      - subroutine 4y ago
        True. I should have said "if you are using a virus"

The number of adenine repeats that confer functional properties is quite variable but it definitely needs to be more than "just 1". I've seen anywhere from 25-250 used in designed plasmids. The exact number people use in their engineered sequence is based on a number of factors, not all of them scientific in nature (e.g. companies charge per basepair synthesize a bespoke polypeptide; e.g. you copied the sequence from a previous clone into ApE and that sequence used 30 repeats and worked fine).

deleted 4y ago
[deleted]
kevviiinn 4y ago
Iirc there's a protein that adds 12-15 slowly then another protein comes in and adds another 200+ when it detects the start of the tail. Not sure about the details about how or why it stops tho. At least when considering mRNA getting prepped for nuclear export
- subroutine 4y ago
  You are probably right, I'm not an expert on this process. But there's likely a difference between the innate eukaryotic cell polyadenylation process vs. how coronavirus accomplishes polyadenylation because coronavirus rna never enters the nucleus.

kolinko 4y ago

In this case it probably works most reliably with around this number of As, and less/more would decrease reliability, butnitmwould still be functional. Most of genetics is like that.

kevviiinn 4y ago
With more As you risk running into the upper limit on sequence length for the virus shell and with less you run the risk of quicker degradation and not enough expression
- subroutine 4y ago
  The first point being only a concern if you are a virus. If instead you are engineering say, an rna vaccine, you could package your transcript into lipofectamine instead of a coronavirus envelope ;) but point taken, there's always an upper limit.
  - kevviiinn 4y ago
    Also a concern when engineering viruses for research or other treatments such as the AAVs
    - subroutine 4y ago
      True. I should have said "if you are using a virus"