When we study yeast, we use a homologous recombination to incorporate our modular tag at the C-terminus of the protein of interest (see for example Knop M et al Yeast 1999, 15, 963-972) at the C-terminus of the genomic sequence of the protein. The tagged proteins are expressed under the control of endogenous promoters.
To express the proteins of interests in human cells we use an in-house modified Flp-In in vivo recombination system from Invitrogen. This system allows us to produce stable cell lines expressing the tagged version of the proteins under the control of a tetracycline inducible promoter. Both cell systems are useful for observing protein localization and purifying protein complexes for their detailed characterization. In the future, however, we would like to add more cell types expressing of the studied proteins.