Why there is a artifical intron in some plasmids? - (Mar/10/2008 )

In some commercially available plasmids, there is a artificial intron between the promotor and the target genes, or one between two fusion genes. Why it is out there? what is its fuction?

Is it related to the RNA splicing or just to help the host recognize the relatively larger fused gene?

Thanks,
Shore

Don't have much time now to come up with literature to cite, but when I did my masters thesis I constructed a reporter-plasmid with an intron-containing luciferase as this was supposed to yield higher expression levels compared to the parental luciferase (in plants that was, but likely the same mechanism might exist in other eukaryotes).

Maybe this is the reason, as the splice-acceptor site will be occupied with splicing machinery that might enhance translation or so?

It's usually to avoid that bacteria produce the active protein. They cannot remove introns, so the protein they would eventually produce will be faulty. You do this when you just want to amplify the plasmid in bacteria but then use it for something else - transforming plants and so, for instance.

Introns is supposed to increased expression by 2-3 fold.

eukaryotes have the TAP proteins, a nuclear mRNA export factor. It binds to the splicing machinary and goes to the nuclear pore.. So as a RNA trascript is spliced it is simultaneously exported out of the nuclease.