A synthetic leucine zipper-based dimerization system for combining multiple promoter specificities

One of the biggest challenges facing gene therapy is the development of Vec tors that direct the activity of therapeutic genes specifically to the site s of disease. To achieve this goal, the restriction of transgene transcript ion via synthetic promoters that are endowed with multiple specificities re presents a particularly promising strategy. Towards this end, we have devel oped a generally applicable strategy (DCTF system) where a synthetic promot er is driven by an artificial heterodimeric transcription factor whose DNA- binding and transactivating subunits are expressed from two promoters with different selectivity. A crucial determinant of the DCTF system is the hete rodimerization interface that should provide for a high affinity interactio n without interference by endogenous proteins. Here, we describe such a dim erization system based on engineered Fos and Jun leucine zippers. We show t he usefulness of this system for the combination of cell type-specific and cell cycle-regulated transcription and demonstrate its functionality in an in vivo setting.