rexB of Bacteriophage λ is an Anti-Cell Death Gene

• Published in: Proceedings of the National Academy of Sciences - PNAS 1998-12, Vol.95 (26), p.15481-15486
• Main Authors: Engelberg-Kulka, Hanna, Reches, Myriam, Narasimhan, Sudarsan, Schoulaker-Schwarz, Rachel, Klemes, Yoel, Aizenman, Einat, Glaser, Gad
• Format: Article
• Language: English
• Subjects: Addiction; Adenosine Triphosphatases - genetics; Adenosine Triphosphatases - metabolism; Amino acids; Apoptosis; Bacteria; Bacteriophage lambda - genetics; Bacteriophages; Biological Sciences; Cell death; Cells; Cloning, Molecular; Endopeptidase Clp; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Escherichia coli - virology; Genes; Genetics; Genotype; Guanylyl Imidodiphosphate - metabolism; Ligases - genetics; Ligases - metabolism; Lysogeny; Mutagenesis, Insertional; Operons; Phage lambda; Phage P1; Plasmids; Prophages; Recombinant Proteins - metabolism; Serine Endopeptidases - genetics; Serine Endopeptidases - metabolism; Starvation; Viral Proteins - genetics; Viral Proteins - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.26.15481

In Escherichia coli, programmed cell death is mediated through ``addiction modules'' consisting of two genes; the product of one gene is long-lived and toxic, whereas the product of the other is short-lived and antagonizes the toxic effect. Here we show that the product of λ rexB, one of the few genes expressed in the lysogenic state of bacteriophage λ , prevents cell death directed by each of two addiction modules, phd-doc of plasmid prophage P1 and the rel mazEF of E. coli, which is induced by the signal molecule guanosine 3′,5′-bispyrophosphate (ppGpp) and thus by amino acid starvation. λ RexB inhibits the degradation of the antitoxic labile components Phd and MazE of these systems, which are substrates of ClpP proteases. We present a model for this anti-cell death effect of λ RexB through its action on the ClpP proteolytic subunit. We also propose that the λ rex operon has an additional function to the well known phenomenon of exclusion of other phages; it can prevent the death of lysogenized cells under conditions of nutrient starvation. Thus, the rex operon may be considered as the ``survival operon'' of phage λ .