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Participation of IHF and a distant UP element in the stimulation of the phage λ P L promoter
Author(s) -
Giladi Hilla,
Koby Simi,
Prag Gali,
Engelhorn Manuel,
Geiselmann Johannes,
Oppenheim Amos B.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.01079.x
Subject(s) - biology , stimulation , element (criminal law) , promoter activity , promoter , genetics , gene , neuroscience , gene expression , political science , law
We have previously identified a UP element in the phage λ P L promoter, centred at position −90 from the transcription start site. Integration host factor (IHF), a heterodimeric DNA‐binding and ‐bending protein, binds upstream of the λ P L promoter in a region overlapping the UP element. Stimulation of transcription by IHF requires an intact αCTD and affects the initial binding of RNA polymerase to the promoter. We propose a model for the stimulation of P L by IHF in which IHF bends the DNA to bring the distal UP sequence in closer proximity to the promoter core sequences to allow the docking of the αCTD of RNA polymerase. Furthermore, IHF may also participate in protein–protein interactions with the αCTD. In support of this model, we found that alanine substitutions in αCTD at positions 265, 268, 270 and 275 reduced P L promoter activity. Mutations in the IHF DNA binding site, as well as IHF mutant proteins exhibiting a decreased ability to bend the DNA, were both defective in stimulating the P L promoter. In addition, some of the mutated IHF residues are clustered at a protein surface that interacts with the UP DNA sequence. These residues may also participate in protein–protein interactions with the αCTD.