Interaction of the Cro repressor with the lysis/lysogeny switch of the Lactobacillus casei temperate bacteriophage A2.
The transcriptional switch region of Lactobacillus casei temperate bacteriophage A2 contains three similar 20 bp operator subsites, O(1), O(2) and O(3), which are interspersed between the divergent promoters P(R) and P(L). The Cro protein binds initially to O(3), which overlaps the -35 region of P(L), excluding the RNA polymerase (sigma(A)-RNAP) from it. This results in the switching off of cI transcription and directs the incoming phage into the lytic cycle. At higher concentrations, Cro also binds to O(1) and/or O(2), which overlap P(R), probably introducing a bend in the intervening DNA. This interaction induces DNA looping, which provokes the subsequent displacement of sigma(A)-RNAP from P(R). Consequently, Cro abolishes the binding of sigma(A)-RNAP to the genetic switch of A2 and, presumably, its own synthesis, contributing indirectly to the entry of phage development into its late stages.
Ladero
Victor
V
Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
García
Pilar
P
Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
Alonso
Juan C
JC
Centro Nacional de Biotecnología, Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain2.
Suárez
Juan E
JE
Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
D004279:DNA, Viral / Q000378:metabolism*; D004268:DNA-Binding Proteins; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D007780:Lacticaseibacillus casei / Q000821:virology*; D008242:Lysogeny; D009875:Operator Regions, Genetic; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins
D004279:DNA, Viral; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D012808:Sigma Factor; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; C063505:RNA polymerase sigma A; D012321:DNA-Directed RNA Polymerases