They inserted these two sequences upstream of a reporter gene and used a colorimetric assay to determine ... create a DNA loop that was as strong as that could be seen in the lac repressor system,” ...

1). In the 'off' state, the Lac inhibitor represses the lac operon, which prevents expression of the Tet repressor and the target gene. Additionally, a short hairpin RNA (shRNA) against the target ...

The operon is regulated by Lac repressor, the product of the lacI gene, which is transcribed from its own promoter (PI). The repressor inhibits transcription by binding to the lac operator (O).