PolyA tails

[Sebastian Cocioba]

What would happen if you make a crazy ling polyA tail. Would it buy the mRNA more time until degradation? Seems like after a given length secondary structures will play a major role...i think? Any thoughts? Is there a limit?

Sebastian S. Cocioba
CEO & Founder
New York Botanics, LLC
Plant Biotech R&D

[Josiah Zayner]

http://scholar.google.com/scholar?hl=en&q=poly+a+tail+length+degradation&btnG=&as_sdt=1%2C5&as_sdtp=

If you want a specific paper that you don't have access to just let me know.

[Cory Tobin]

Maybe but maybe not. The poly(a) tail does more than just prevent
degradation. It interacts with the ribosome and the 5' UTR complex to
control the efficiency/rate of translation. Making the tail too long
may disrupt translation, although I can't find any evidence that it
does in the literature. I'm just speculating that there may be
unintended consequences to lengthening the tail.
Here's a good review on the subject:
http://www.ncbi.nlm.nih.gov/pubmed/22664985 email me if you need the
pdf.

Also, I don't know of any way to actually increase the length of the
tail since it's not coded in the DNA. Well, it sort of is. The
affinity of the poly(A) polymerase, CPSF and PABII for the mRNA
probably effect the length of the tail and those proteins are coded
for in the DNA. But you know what I mean. There isn't a stretch of
poly(T) in the DNA downstream of the CDS that get transcribed into the
tail.

I think there's ways of extending it in vitro. So if you're planning
on injecting mRNA into a cell, that could possibly work. But I
figured you were talking about engineering a (plant?) cell to produce
a long-living mRNA.

-cory

[Sebastian Cocioba]

Yes, but also I noticed that the CaMV in pGreenII 0049 is terminated
with a polyA instead of the usual tnos or other defined terminator. Is
that a kind of preadenylation or just coincidental that it also
terminates CaMV well. SnapGene has the plasmid in its vector directory
and it anotated a polyCap of sorts in the DNA.

Sebastian S. Cocioba
CEO & Founder
New York Botanics, LLC

Plant Biotech R&D From: Cory Tobin
Sent: 3/20/2014 3:24 PM
To: diybio
Subject: Re: [DIYbio] PolyA tails

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[Cory Tobin]

I'm not seeing any long stretch of polyA or polyT anywhere in that
plasmid. In snapgene the feature is called "CaMV poly(A) signal" but
it doesn't actually have a stretch of A's or T's, aside from the 4
consecutive A's starting at position 2961. But of course that would
be transcribed to UUUU.

-cory

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Cory Tobin
Graduate Student
Caltech :: Biology
cto...@caltech.edu
805-443-4702
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