If a  scientist has inserted a non -bacterial gene into a bacterial host and is looking for expression of this foreign gene, which signals are to be provided by this respective vector?

The three most important signals for E. coli genes are promoter,terminator and ribosomal binding site.

Explanaiton:

If a foreign (i.e., non-bacterial) gene is simply ligated into a standard vector and cloned in E. coli, it is very unlikely that a significant amount of recombinant protein will be synthesized. This is because expression is dependent on the gene being surrounded by a collection of signals that can be recognized by the bacterium. These signals, which are short sequences of nucleotides, advertise the presence of the gene and provide instructions for the transcriptional and translational apparatus of the cell.