How to control cloned cDNA expression level in cells? - (Feb/27/2009 )

If I want to overexpress a gene in a cell, by transfection (using lipo2k)

And I don't want to have too high expression of it (cos that might not tell me the physiologic effect of the gene)

Can I monitor the dosage of the protein in the cell by changing to amount of plasmid I mix with lipo2k?

My question is basically this:

If I change the amount of plasmid I add, which of the following would most likely change:

1. Transfection efficiency?
2. Expression level of my target gene?
3. Nothing?

Try making stable cell lines to get higher expression which can be a little over the base line. With transient transfection one may have for eg. 1000x over expression.

If you change the amount of plasmid for transfection, you can have a change in transfection efficiency and also expression level.

stable cell line is not an option

I'm doing primary cell culture, and I've never passage the cell (not able to)

any thoughts?

Hi,

What kind of a promoter are you using? If it is a viral promoter the expression will be very high...maybe choose a weak promoter?

Stardust

jiro_killua on Mar 1 2009, 06:46 AM said:

you could infect cells with viral particles, (Lentivirus, AAV) coding for the trangene and use a weak promoter to get a low level expression.

stardust on Mar 1 2009, 03:20 AM said:

now is CMV promoter....

CMV is very strong, I don't think you will ever get "physiological" levels of protein expression even if you had the option for making a stable line...can't recommend a promoter now since I don't know which cells you are using...

Stardust

stardust on Mar 1 2009, 02:16 PM said:

I'm using hepatocytes isolated from fetal mice

Thanks a lot

we often use PGK promoter (phosphoglycerate kinase) in our cells, it is strong as well but not as strong as CMV...otherwise google for weak promoters, many people will use nonviral promoters...or maybe find a promoter that is specific for hepatocytes..

Stardust