Antirepression as a second mechanism of transcriptional activation by a minor groove binding protein.
Competence for genetic transformation in the bacterium Bacillus subtilis is a bistable differentiation process governed by the minor groove DNA binding protein ComK. No detectable comK transcription occurs in the absence of an intact comK gene, indicating that ComK has auto-activating properties. ComK auto-stimulation, which is dependent on ComK binding to the comK promoter, is a critical step in competence development, ensuring quick and high-level expression of the late-competence genes. Auto-stimulation is also essential for the bistable expression pattern of competence. Here, we demonstrate that ComK acts as an activator at its own promoter by antagonizing the action of two repressors, Rok and CodY. Importantly, antirepression occurs without preventing binding of the repressing proteins, suggesting that ComK and the repressors might bind at distinct surfaces of the DNA helix. DegU, a DNA binding protein known to increase the affinity of ComK for its own promoter, potentiates the antirepression activity of ComK. We postulate that antirepression is primarily achieved through modulation of DNA topology. Although to our knowledge ComK is the only DNA binding protein shown to act in this novel fashion, other minor groove binding proteins may act similarly.
Smits
Wiep Klaas
WK
Department of Genetics, University of Groningen, Kerklaan 30, 9751NN, Haren, The Netherlands.
Hoa
Tran Thu
TT
Hamoen
Leendert W
LW
Kuipers
Oscar P
OP
Dubnau
David
D
D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites / Q000187:drug effects; D002865:Chromomycins / Q000494:pharmacology; D004269:DNA, Bacterial / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D008739:Methyl Green / Q000494:pharmacology; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation / Q000187:drug effects; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012097:Repressor Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000187:drug effects
D001426:Bacterial Proteins; D002865:Chromomycins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C087449:comK protein, Bacillus subtilis; D008739:Methyl Green; D012321:DNA-Directed RNA Polymerases