Advances and current limitations in transcript-level control of gene expression.

Gene expression control is critical to increase production of recombinant proteins, fine-tune metabolic pathways and reliably express synthetic pathways. The importance of transcriptional control seems to be most important in eukaryotic systems. In this review, we highlight recent developments in the field of transcriptional engineering with an emphasis on the opportunities and challenges. We discuss the engineering of 'parts' that influence transcriptional throughput including promoters, terminators, and transcription factors as well as the genetic context of the expression cassette. While great strides have been made in the area, the robustness of these parts has been largely untested. This review highlights the importance of considering robustness in biological systems and the limitations that current synthetic parts possess.