Transcript Chapter 4

10.3 Eukaryotic gene control: purposes
and general principles
 Unlike bacterial cells and most single cell eukaryotes, cells in
multicelular organisms have relatively few genes that are
reversibly regulated by environmental conditions
 However, gene control in multicellular organisms is important
for development and differentiation, and is generally not
reversible
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10.3 Many genes in higher eukaryotes are
regulated by controlling their transcription
The nascent chain (run-on)
assay allows measurement
of the rate of transcription of
a given gene
Figure 10-22
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10.3 Differential synthesis of 12 mRNAs
encoding liver-specific genes
Figure 10-23
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10.3 Regulatory elements in eukaryotic DNA
often are many kilobases from start sites
 The basic principles that control transcription in bacteria also
apply to eukaryotic organisms: transcription is initiated at a
specific base pair and is controlled by the binding of transacting proteins (transcription factors) to cis-acting regulatory
DNA sequences
 However, eukaryotic cis-acting elements are often much
further from the promoter they regulate, and transcription
from a single promoter may be regulated by binding of
multiple transcription factors to alternative control elements
 Transcription control sequences can be identified by analysis
of a 5-deletion series
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10.3 Construction and analysis of a 5-deletion
series
Figure 10-24
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10.3 Analysis of labeled nascent transcripts
allows mapping of the transcription-initiation site
Figure 10-28
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10.3 RNA polymerase II initiates transcription at DNA
sequences corresponding to the 5 cap of mRNAs
“Runs off”
“Runs off”
“Runs off”
Figure 10-29
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10.4 The TATA box is a highly conserved
promoter in eukaryotic DNA
Alternative promoters in eukaryotes include initiators and CpG islands
5’-YYA+1N-T/A-YYY-3’ (Y=C/T)
Figure 10-30
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10.4 Identification of transcription-control
elements with linker mutants
Figure 10-31
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10.4 Promoter-proximal elements help
regulate eukaryotic genes
Figure 10-32
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10.4 Transcription by RNA polymerase II
often is stimulated by distant enhancer sites
Identification of the SV40 enhancer region
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Figure 10-33
10.4 Most eukaryotic genes are regulated by
multiple transcription control mechanisms
Figure 10-34
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10.5 Transcription factors may be identified
by biochemical techniques
Figure 10-35
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10.5 In vivo assay for transcription factor activity
Figure 10-37
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10.5 A series of Gal4 deletion mutants demonstrated
that transcription factors are composed of separable
DNA-binding and activation domains
Figure 10-38
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10.5 Transcriptional activators are modular proteins
composed of distinct functional domains
Figure 10-39
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10.5 DNA-binding domains can be classified
into numerous structural types
 Homeodomain proteins
 Zinc-finger proteins
 Winged-helix (forkhead) proteins
 Leucine-zipper proteins
 Helix-loop-helix proteins
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10.5 Homeodomain from Engrailed protein interacting
with its specific DNA recognition site
Figure 10-40
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10.5 Interactions of C2H2 and C4 zinc-finger
domains with DNA
Figure 10-41
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10.5 Interaction between a C6 zinc-finger
protein (Gal4) and DNA
Figure 10-42
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10.5 Interaction of a homodimeric leucine-zipper
protein and DNA
dimerização assegurada pela interacção dos
a.a. Hidrofóbicos (ex:leucina) espaçados
regularmente
Figure 10-43
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10.5 Interaction of a helix-loop-helix in a
homodimeric protein and DNA
Figure 10-44
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10.5 Heterodimeric transcriptional factors
increase gene-control options
Figure 10-45
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10.5 Activation domains exhibit considerable
structural diversity
Figure 10-47
Figure 10-46
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10.5 Multiprotein complexes form on enhancers
Figure 10-48
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10.5 Many repressors are the functional
converse of activators
 Eukaryotic transcription is regulated by repressors as well as
activators
 Repressor-binding sites can be identified and repressors
purified by the same techniques used for activators
 Many eukaryotic repressors have two domains: a DNAbinding domain and a repressor domain
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10.6 RNA polymerase II transcriptioninitiation complex
 Initiation by Pol II requires general transcription factors, which
position Pol II at initiation sites and are required for
transcription of most genes transcribed by this polymerase
 General transcription factors are multimeric and highly
conserved
 Proteins comprising the Pol II transcription-initiation complex
assemble in a specific order in vitro but most of the proteins
may combine to form a holoenzyme complex in vivo
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10.6 Stepwise assembly of Pol II
transcription-initiation complex in vitro
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Figure 10-50
10.6 The conserved C-terminal domain of
TBP binds to TATA-box DNA
TBP is a subunit of TFIID
Figure 10-51
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10.6 Structural model of the complex of
promoter DNA, TBP, TFIIB, and Pol II
Figure 10-53
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10.7 Activators stimulate the highly
cooperative assembly of initiation complexes
Binding sites for activators that control transcription of the mouse TTR gene
Figure 10-60
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10.7 Model for cooperative assembly of an activated
transcription-initiation complex in the TTR promoter
Figure 10-61
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10.7 Repressors interfere directly with
transcription initiation in several ways
Figure 10-62
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10.7 Lipid-soluble hormones control the
activities of nuclear receptors
Figure 10-63
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10.7 Domain structure of nuclear receptors
Figure 10-64
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10.7 Response elements are DNA sites that
bind several major nuclear receptors
Figure 10-65
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10.7 Model of hormone-dependent gene
activation by the glucocorticoid receptor
Figure 10-67
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10.7 Polypeptide hormones signal
phosphorylation of some transcription factors
Model of IFN-mediated
gene activation by
phosphorylation and
dimerization of Stat1
Figure 10-68
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10.8 Transcription initiation by Pol I and
Pol III is analogous to that by Pol II
Figure 10-69
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10.8 Other transcription systems
 T7 and related bacteriophages express monomeric, largely
unregulated RNA polymerases
 Mitochondrial DNA is transcribed by RNA polymerases with
similarities to bacteriophage and bacterial enzymes
 Transcription of chloroplast DNA resembles bacterial
transcription
 Transcription by archaeans is closer to eukaryotic than to
bacterial transcription
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