(489ak) Nucleoid Structuring Proteins and Combinatorial Regulation in Bacterial Gene Expression

A number of bacterial promoters are subject to combinatorial regulation, where the expression of these promoters is dependent upon the activity of multiple transcription factors. In the case of bacteria, the general mechanism for combinatorial regulation is still unknown as it is not clear how the binding of multiple factors, often at distal locations, can affect the rate of open complex formation. We hypothesize that nucleoid silencing proteins such as H-NS play a central role in mediating combinatorial regulation.

In this work, we explored the role of nucleoid silencing using the blg promoter from E. coli as our model. This promoter is flanked by two silencer sequences that serve as nucleating sites for H-NS. Previously, it has also been shown that silencing can be relieved by insertion of LacI or λ operator sites within the bgl upstream silencer. Here, we investigated this silencing mechanism further by introducing multiple operator sites within the blg promoter to engineer combinatorial regulation. We also explored how these silencing sequences can be used to regulate other promoters. Collectively, these results represent a first step toward using nucleoid structuring proteins as a tool for engineering complex regulation in bacterial.