FIS activates sequential steps during transcription initiation at a stable RNA promoter.
FIS (factor for inversion stimulation) is a small dimeric DNA-bending protein which both stimulates DNA inversion and activates transcription at stable RNA promoters in Escherichia coli. Both these processes involve the initial formation of a complex nucleoprotein assembly followed by local DNA untwisting at a specific site. We have demonstrated previously that at the tyrT promoter three FIS dimers are required to form a nucleoprotein complex with RNA polymerase. We now show that this complex is structurally dynamic and that FIS, uniquely for a prokaryotic transcriptional activator, facilitates sequential steps in the initiation process, enabling efficient polymerase recruitment, untwisting of DNA at the transcription startpoint and finally the escape of polymerase from the promoter. Activation of all these steps requires that the three FIS dimers bind in helical register. We suggest that FIS acts by stabilizing a DNA microloop whose topology is coupled to the local topological transitions generated during the initiation of transcription.
Muskhelishvili
G
G
Institut für Genetik und Mikrobiologie, LMU, München, Germany.
Buckle
M
M
Heumann
H
H
Kahmann
R
R
Travers
A A
AA
D002352:Carrier Proteins / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D012365:RNA, Transfer, Tyr / Q000235:genetics*; D015533:Transcriptional Activation
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D035021:Factor For Inversion Stimulation Protein; D034982:Integration Host Factors; D012365:RNA, Transfer, Tyr; C440502:integration host factor, E coli; D004247:DNA; D012321:DNA-Directed RNA Polymerases