A series of bidirectional tetracycline-inducible promoters provides coordinated protein expression.

Coordinated control of protein expression is highly desirable for functional genomics. Here we show a widely applicable approach to construction and use of custom bidirectional promoters capable of reproducible coexpression of two proteins. The use of a bidirectional promoter system overcomes many of the limitations of current coexpression systems such as unpredictable upstream and downstream expression ratios mediated by an internal ribosome entry site. We present examples of tetracycline-inducible, bidirectional promoter systems that produce simultaneous and rapid coinduction of two separate reporters to predictable levels and ratios. Steric blocking of transcription initiation by simple tetracycline repressors, rather than the use of transcriptional activator/repressor domain fusions, makes the system described here superior for investigating downstream transcriptional consequences of protein expression.