Role of operator subsites in Arc repression.
By binding to adjacent subsites in its 21 base-pair operator, Arc represses transcription from two divergent promoters, Pant and Pmnt, in the immunity I operon of bacteriophage P22. Arc dimers bind to each subsite with nanomolar affinities and interact through protein-protein interactions to stabilize binding further. Here, we show that an Arc dimer bound to a single subsite reduces the rate of RNA polymerase open-complex formation and represses transcription from Pant and Pmnt promoter variants to varying degrees. Occupancy of the subsite proximal to the Pant-35 region results in significantly greater repression than occupancy of the- 10 proximal subsite. For repression of Pmnt, Arc bound at the- 10 proximal subsite is more effective than Arc bound at the- 35 proximal subsite. Because of the divergent orientations of the two promoters, the-35 proximal site in Pant is the same as the- 10 proximal site in Pmnt. Thus, in both cases, the same operator subsite is primarily responsible for repression of transcription initiation.
Smith
T L
TL
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA.
Sauer
R T
RT
D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000032:analysis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins
D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; D004247:DNA