While genetic engineering has undergone rapid advancement with the discovery of CRISPR / Cas9, there is room for improvement for genetic circuit control, precision (reducing circuit ‘leakiness’) and delivery into living systems. The claimed invention offers programmable and precise regulation of dCas9 functions in response to multiple molecular signals by using synthetic gene circuits, greatly expanding applications. Moreover, using the system to greatest therapeutic potential has been greatly limited by the restrictive cargo size of existing viral delivery systems. By splitting dCas9 into multiple sections, the delivery size of synthetic gene circuits is greatly reduced. By exchanging split dCas9 domains, differential regulation on one gene, or activating two different genes in response to cell-type specific microRNAs is illustrated. Practical applications of the illustrative examples include engineered sensory switches including indicators for bladder cancer as well as enhanced systems for adenovirus delivery, cellular regulation, plant cell modification and potential therapeutic applications.