The invention relates to the use of a skin permeating compound such as phloretin for controlling transgene expression under control of the Pseudomonas putida DOT-T1E-derived bacterial repressor TtgR, to a vector comprising the genetic code for the repressor TtgR fused to a transactivation or a transrepressor domain, to a vector comprising a TtgR-specific operator sequence (OTtgR), a promoter and a polynucleotide coding for an endogenous or exogenous protein, and to a mammalian cell transiently or constitutively transfected with the mentioned vectors, and to mammals comprising such cells in nano- or microcontainers.