Regulatory factors acting at the bacteriophage Mu middle promoter.
Lytic development of bacteriophage Mu proceeds through three phases of transcription: early, middle, and late. Initiation of middle transcription from Pm requires the phage-encoded activator, Mor. An examination of the sequences surrounding the promoter revealed possible binding sites for Mu proteins A and c, as well as for Escherichia coli integration host factor. Promoter fragments containing 5' and 3' deletions were fused to the lacZ reporter gene and assayed for activity after induction of a Mu prophage or a plasmid-borne mor gene. Sequences upstream of position -62 and downstream of +10 were dispensable for promoter activity. In DNase I footprinting with both crude extract and purified protein, Mor protected Pm sequences from position -56 to -33. Mutations disrupting the dyad symmetry of the terminator of early transcription overlapping the Mor binding site did not reduce promoter activity, suggesting that the symmetry per se is not required for Mor binding or Pm activation. Purified Mu lysogenic repressor (c) also bound to Pm, overlapping the Mor binding site. Production of large amounts of repressor in vivo reduced Mor-dependent promoter activity nearly 10-fold. Promoters with mutations in the repressor binding site showed a reduction in this repressor-mediated inhibition of Pm activity.
Kahmeyer-Gabbe
M
M
Department of Microbiology and Immunology, University of Tennessee-Memphis 38163, USA.
Howe
M M
MM
D010583:Bacteriophage mu / Q000235:genetics* / Q000254:growth & development; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000821:virology; D015967:Gene Expression Regulation, Viral; D008242:Lysogeny / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011993:Recombinant Fusion Proteins; D012091:Repetitive Sequences, Nucleic Acid; D012097:Repressor Proteins / Q000378:metabolism; D017384:Sequence Deletion; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins