Enterobacteria takeover by phage infection – TakeoverBac

At the onset of infection, bacteriophage viruses (or phages) defeat bacterial defenses and hijack cellular functions to propagate inside their hosts. A century after phages were discovered and despite many scientific breakthroughs in phage research, the early mechanisms of host takeover during infection are still poorly understood. Bacteriophage T5 uses a unique two-step DNA delivery mechanism that offers an exceptional opportunity to investigate host takeover uncoupled from the downstream phage multiplication steps. Phage genes responsible for subverting host functions are expressed before the complete genome enters the host, and infection can be frozen at this stage. The takeover mechanism of E. coli by T5 is characterized by rapid host DNA degradation and a shutoff of early phage gene transcription before the second step DNA transfer resumes (SST). Two conserved proteins, A1 and A2, were found to be essential for these early events and to control the SST. However, the function of these multitasking proteins had remained enigmatic for 50 years. We recently uncovered the nuclease activity of A1 and the transcriptional regulatory function of A2. TakeoverBac project proposes a multidisciplinary and integrative study of A1 and A2 early phage proteins. We will combine in vitro and in vivo functional investigations to: i) Understand how A1 nuclease activity destroys the host chromosome and if this activity controls the restart of T5 DNA delivery. ii) Establish the transcriptional chronology of phage and host gene transcription orchestrated by A2. iii) Identify A1 and A2 protein partners that are essential for infection. The TakeoverBac consortium brings together a strong expertise in phage biology, biochemistry, bacterial genetics and structural biology to investigate these aspects at the molecular and cellular level. Taken together, this project should identify vital host functions targeted by T5 proteins. In the context of the alarming rise in antibiotic multiresistance and lack of new antibiotic molecules, this study will initiate new axes of research with potential therapeutic applications. Thus the fundamental scientific output of this research will provide a framework to develop phage-inspired tools useful in research and in the fight against bacterial infections.