Synthetic Transcription Factors Switch from Local to Long-Range Control during Cell Differentiation.

Genes, including promoters and enhancers, are regulated by short- and long-range interactions in higher eukaryotes. It is unclear how mammalian gene expression subject to such a combinatorial regulation can be controlled by synthetic transcription factors (TF). Here, we studied how synthetic TALE transcriptional activators and repressors affect the expression of genes in a gene array during cellular differentiation. The protocadherin gene array is silent in mouse embryonic stem (ES) and neuronal progenitor cells. The TALE transcriptional activator recruited to a promoter activates specifically the target gene in ES cells. Upon differentiation into neuronal progenitors, the transcriptional regulatory logic changes: the same activator behaves like an enhancer, activating distant genes in a correlated, stochastic fashion. The long-range effect is reflected by the alterations in CpG methylation. Our findings reveal the limits of precision and the opportunities in the control of gene expression for TF-based therapies in cells of various differentiation stages.