VP22 Voyager - TAT

Tue Feb 23 09:21:34 EST 1999

>Dear David (and other netters):
>While I'm sure that the GFP-VP22 fusion must work, or Invitrogen
>wouldn't sell it, you might want to be aware of a paper claiming to be
>unable to replicate the work of Elliot and O'Hare:
>B Fang, B Xu, P Koch, JA Roth "Intercellular trafficking of VP22-GFP
>fusion proteins is not observed in cultured mammalian cells" Gene
>Therapy (1998) 5:1420-1424
>Any comments by others that have worked with VP22?

Interesting reference.  I hope they were able to show that the VP22-GFP
did work in other cells as a positive control.  I have not used any of
these protein transduction systems, but have followed them with wonder.
I'd like to add that Steve Dowdy here at Wash U has been using a similar
strategy with a small translocating peptide (10 or 11 aa) from HIV TAT
to deliver things to cells.  He published at least a couple of Nature
Biotechnology articles on his methods last year.  As I recall, proteins
must be denatured in order to be transduced, and are then refolded in
vivo.  Based on Steve's results, it appears that the TAT system does
not utilize a specific receptor intake system, as these things get in
even in the cold.  This might imply that the TAT peptide itself interacts
with membranes and mediates the translocation.  It'd be interesting to
know how this works, such as what types of lipids or proteins are required,
etc., which could be addressed by in vitro experiments.  Also, what types
of cells can be transduced? For instance, yeast spheroplasts?  If so, one
could imagine transducing a toxin in order to examine the genetics
behind this system.  Well, just some thoughts on these strange creatures.
I would add though that the TAT system may be a simpler choice for people
unwilling to trust in an Invitrogen kit, since these constructs can be made
by inserting a small linker to most anything.  Oh wait, I think there's a
patent lawyer on the phone for me now, I better get outta here....

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