Without knowing the exact system that you plan to use, I'm not sure whether I'm directly addressing your question. Here, I assume that you meant to say "transduction" with actual virus, not transfection with viral plasmid. You can easily transduce pri-miRNA using lentivirus into cells. Expression duration depends on your cell type and promoter. You can clone pri-miRNAs using genomic DNAs. Several companies are selling pri-miRNAs in lentiviral vector and some even sells premade virus.

Thank you for your considerations. You are right, I should saiy "transduction" instead of transfection. Can you tell me wich companies sell this assay? I have already tried but could not find any. I am looking forward to use THP-1 cells in this system.

In my lab, we always clone by ourselves. So we have not tried the commercial ones. Two that I know are OriGene and Systems Biosciences. I have read several articles using both companies pre-made pri-miRNAs. Good luck! PS) We have been using BV2 cells and also plan to use THP-1 cells in our miRNA project.

I've transfected pre-miRs using Applied Biosystems products, i.e: pre-miRs, and using the transfection reagent siPORT Neo Fx. Works very well.

I know that Clonetech sells inducible systems (TetOn) of the miR you need, but I have not experience using them.

@Martin: Watch out! Applied Biosystems/Ambions "pre-miRs" are in fact mature miRNA mimics, i.e. double stranded oligonucleotides similar in structure to siRNAs. They don't need further processing and are loaded directly into RISC. Don't know why they called it "pre-miR", because it only causes confusion. I don't think there are precursor mimics for transient transfection. Transduction is the way to go.

@Gert, pre-miR-s from ABI are indeed pre(cursor)-miRs, are the stem loop form; they are not mature and are cut to the mature form before being loaded into RISC. They have a lenght of about 70 mers and are double stranded. They can be used only as transient transfection, of course. They now have a new product which are miRNA mimics which are already mature, but they still offer the pre-miR first generation product.

@Martin Check the product description in attachment. The different resources on the product are ambiguous, that's why we contacted tech support.

Also, this is the product description on the website: "Ambion® Pre-miR™ miRNA Precursor Molecules are small, chemically modified double-stranded RNA molecules designed to mimic endogenous mature miRNA molecules."

@ Martin & Gert. I also called the tech support regarding this confusing product name about 3 years ago. I was told that what they are selling is in fact "mature" miRNA, not "Pre-mir".