Retrovirus with LTR-polyA-LTR = garbage?

[Nicolas Kuperwasser]

wolfsc at ibms.sinica.edu.tw ("Wolfgang Schechinger") wrote in message news:<3C85266E.8311.2B22F2 at localhost>...
> Dear all, 
> 
> Luk Vandenberghe who recently replied to my retrovirus problem questions this 
> NG just pointed me to a possible problem when having a retroviral construct 
> like this:
> 
> ---pLHCX-backbone-----5'LTR--PSI--HygR--CMV--cDNA-STOP--polyA--3'LTR---
> 
> The presence of polyA between the LTRs could lead to premature termination of 
> transcription and thus not yield (at least not high titers of) active 
> retrovirus. Sounds obvious. 
> 
> When transfecting such a construct into packaging cells, then I would be able 
> to detect protein expression there, but not get high titer virus.
> In consequence when using lacZ as reporter in such a construct, I also would 
> detect less "transfected" packaging cells due to less self-infection (in 
> comparison to a construct that doesn't have the polyA feature).
> 
> Comments and references are extremely welcome.
> 
> Regards,
> Wo
Question...is the polyA a trac of polyA or the cis-element signalling
for polyA'tion to occur?  My feeling is that a strech of A's will not
affect the proper processing of the RNA and subsequent virus
formation, but a cis-element will pretty much muck up virus
construction.


Nick