Corynebacterium glutamicum WhcD interacts with WhiA to exert a regulatory effect on cell division genes

Corynebacterium glutamicum WhcD plays an important regulatory role in cell division. Binding of WhcD to the promoter region of its target genes, such as ftsZ, was observed by electrophoretic mobility shift assays (EMSA) using purified fusion proteins; however, binding could only be observed in the presence of WhiA. Although WhcD alone did not bind to the DNA, it stimulated binding of WhiA to the promoter region of the cell division gene ftsZ. Binding of WhcD and WhiA to DNA did not occur in the presence of the oxidant diamide. Purified WhcD and WhiA physically interacted in vitro. The presence of diamide did not disrupt the WhcD-WhiA interaction but affected binding of WhiA to the promoter region of ftsZ. The GACAC motif and adjacent sequences were found to be important for binding of the WhcD-WhiA complex to the DNA. Collectively, our results suggest that WhcD enhances the WhiA DNA-binding activity by physically interacting with WhiA. In addition, loss of WhiA DNA-binding activity in the presence of an oxidant agent may suggest a role for this protein as a switch that controls cell division in cells under oxidative stress.