title: Interaction of the Cro repressor with the lysis/lysogeny switch of the Lactobacillus casei temperate bacteriophage A2.
abstract: 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.
authors.affiliation: Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
authors.forename: Victor
authors.initials: V
authors.lastname: Ladero
authors.affiliation: Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
authors.forename: Pilar
authors.initials: P
authors.lastname: García
authors.affiliation: Centro Nacional de Biotecnología, Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain2.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Alonso
authors.affiliation: Area de Microbiología, Facultad de Medicina, Universidad de Oviedo, Julián Clavería s. n., 33006 Oviedo, Spain1.
authors.forename: Juan E
authors.initials: JE
authors.lastname: Suárez
mesh_terms: 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
chemical_list: 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