Chapter 10
Regulation of Transcription Initiation
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10.1 Bacterial gene control: the JacobMonod model
Figure 10-2
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10.1 Experimental evidence for cis-acting
DNA sequences
Figure 10-3
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10.1 Experimental evidence for transacting genes/proteins
Figure 10-4
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10.2 Bacterial transcription initiation
 RNA polymerase initiates transcription of most genes at a
unique DNA position lying upstream of the coding sequence
 The base pair where transcription initiates is termed the
transcription-initiation site or start site
 By convention, the transcription-initiation site in the DNA
sequence is designated +1, and base pairs extending in the
direction of transcription (downstream) are assigned positive
numbers which those extending in the opposite direction
(upstream) are assigned negative numbers
 Various proteins (RNA polymerase, activators, repressors)
interact with DNA at or near the promoter to regulate
transcription initiation
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10.2 DNase I footprinting assays identify
protein-DNA interactions
Figure 10-6
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10.2 Gel-shift assays identify protein-DNA
interactions
Figure 10-7
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10.2 The footprint of RNA polymerase and
lac repressor on the lac control region
Figure 10-8
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10.2 The lac control region contains three
critical cis-acting sites
Figure 10-9
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10.2 RNA polymerase binds to specific
promoter sequences to initiate transcription
Each subunit has a specific function
Figure 10-10
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10.2 Differences in E. coli promoter sequences
affect the frequency of transcription initiation
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Figure 10-11
10.2 Most operator sequences are short
inverted repeats
The lac operator
Figure 10-12
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10.2 Most bacterial repressors are dimers containing
 helices that insert into adjacent major grooves of
operator DNA
Figure 10-13
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10.2 Ligand-induced conformational changes
alter affinity of many repressors for DNA
Tryptophan binding
induces a
conformational change
in the trp aporepressor
Figure 10-14
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10.2 Positive control of the lac operon is
exerted by cAMP-CAP
CAP = catabolite
activator protein
Figure 10-16
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10.2 Cooperative binding of cAMP-CAP and RNA
polymerase to the lac contol region activates
transcription
Figure 10-17
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10.2 Transcription from some promoters
is initiated by alternative sigma () factors
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10.2 Activation of 54-containing RNA
polymerase at glnA promotor by NtrC
Figure 10-19
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10.2 Visualization of DNA looping and
interaction of bound NtrC and 54- polymerase
Figure 10-20
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10.2 Many bacterial responses are controlled
by two-component regulatory systems
The PhoR/PhoB two-component regulatory system in E. coli
Figure 10-21
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