Help: SP6/T7 specificity

[Peter Schuchert]

How specific are SP6 and T7 RNA polymerase concering the other
promoter sequences?

I use RNA trancripts as in situ probes, generated from an cDNA
with flanking T7 and SP6 promoters. The antisense probe gives
me a very strong signal in the expected cell population. However,
also the sense probe gives a signal in the same cells, although 
much much weaker.
I inerpreted this that by generating my sense probe with SP6,
also some transcripts are formed from the T7 site and producing.

Has anyone made similar observations? 

 
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Dr. P. Schuchert
University Hospital INSEL
Dept. Gastroenterology,  MEM-B814
CH-3010 Bern Switzerland
Tel 0041 31 632 84 92    Fax 0041 31 632 96 65
http://www.unibas.ch/dib/zoologie/research/schuch.html
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