The BZLF1 promoter of Epstein-Barr virus is controlled by E box-/HI-motif-binding factors during virus latency.

The BZLF1 open reading frame of Epstein-Barr virus (EBV) encodes an important transactivator of replication. During latency, transcription of this gene is switched off. HI motifs have been shown to cause negative regulation of the promoter.

A C-terminal 18 amino acid deletion in MarR in a clinical isolate of Escherichia coli reduces MarR binding properties and increases the MIC of ciprofloxacin.

As described recently, the different degree of fluoroquinolone resistance in a pair of sequential clinical isolates of Escherichia coli was due to the increased expression of the regulatory gene marA as a consequence of an 18 amino acid C-terminal deletion in the repressor MarR (MarR Delta). To further investigate the molecular mechanism of the loss of repressor function, we purified recombinant wild-type and mutated MarR, and tested their respective ability to form dimers and their specific DNA binding properties to the operator region marO. The dimerization capacity was analysed by non-reducing SDS-PAGE and by disuccinimidyl suberate-mediated cross-linking of the recombinant proteins.