The pcDNA3.1 vector is an extremely popular and highly efficient vector for mammalian transient and stable transfections. I would recommend using that as your backbone.

Thanks a lot Jordan! I had a look at it , and it seems like this is what we want.

For the cell type, CHO and 293 cells are quite good for production of intracellular proteins, especially when your molecules require some post-transcriptional modifications. One more advantage of these cells is that they are easily transfected with the cost-effective polyethylenimine (PEI), a good option when you do thaousands of transfections...!!!