Inhibition of prokaryotic cell growth by HIV1 Vpr

We have cloned the nef, vif, vpr and vpu genes of HIV1 in the pGEX system to produce auxiliary proteins of HIV1 as N-terminal fusions with glutathione S-transferase (GST). Some GST proteins are difficult to obtain under standard conditions. The synthesis and solubility varied considerably from one protein to another. We investigated the reasons for the poor production of GST-Vpr, GST-Vpu and GST-Vif. Interestingly, using this GST prokaryotic model, we demonstrated that Vpr, which is known to block the cell cycle of mammalian and yeast cells at the G2 phase, is also bacteriostatic for Escherichia coli. The effect on E. coli was specific to Vpr, and was not linked to the expression of the other HIV1 proteins. This suggests that Vpr interferes with components of cell replication that are conserved from prokaryotes to eukaryotes. Thus, E. coli appears to be a convenient model system for studies on the function of Vpr.