1. Chapter 10: transcriptional regulation
Fig. 10-1

2. Regulation of Gene Transcription
DNA-binding proteins
RNA polymerase binding to the transcription
initiation site (e.g., promoter)
Regulatory protein(s) binding to other sites
(e.g., operator)
Regulatory protein binding can positively or
negatively regulate transcription

3. Positive/negative regulation:
binding of activator or repressor proteins
Fig. 10-2

4. Regulation of Gene Transcription
DNA-binding proteins
RNA polymerase binding to the transcription
initiation site (e.g., promoter)
Regulatory protein(s) binding to other sites
(e.g., operator)
Regulatory protein binding can positively or
negatively regulate transcription
Protein affinity for DNA or for other proteins can
be influenced by allosteric conformation

5. Effector binding mediates allosteric change
Effector promotes activator binding
Effector prevents repressor binding
Fig. 10-3

6. In mammalian newborns, lactose is the principal sugar source for
Fig. 10-5
In mammalian newborns, lactose
is the principal sugar source for
intestinal flora

7. Lactose utilization by E. coli
-linked disaccharide peculiar to milk
lac genes encode a glycosidase and proteins
that promote cellular import of lactose
Genes are transcribed only in the presence of
lactose (inducible) and the absence of glucose
(catabolite repression)
Genes are organized into a co-transcribed cluster
(operon; encodes a polycistronic mRNA)

8. (simplified schematic)
lac operon in E. coli
(simplified schematic)
Fig. 10-4

9. lac operon in E. coli (dynamic schematic)
Fig. 10-6

11. Fig. 10-8

13. Fig. 10-9

15. Fig

16. Effects of mutations within consensus sequences of E. coli promoters
Fig

17. Effects of lac operator mutations
Fig

18. E. coli lac is also regulated by catabolite repression
Regulates preferential utilization of glucose
Mediated by cAMP (glucose-responsive)
cAMP is effector of catabolite activator protein (CAP)
cAMP-CAP binds to lac promoter, enhancing
binding of RNA polymerase

19. Fig

20. Fig

21. Activated CAP binding induces a distortion of its DNA binding site
“presents” P region
to RNA polymerase
Fig

22. Molecular organization of the lac promoter region
Fig

23. Cumulative regulatory control of lac transcription
Fig

24. Cumulative regulatory control of lac transcription
Fig

25. “Negative control” (repression) “Positive control” (activation)
Fig

26. Typical 5’ end sequences found in eukaryote genes
(promoter and nearby elements)
RNA polymerase
binding site
Fig

27. β-globin promoter region and effects of mutation
Consensus sequences predict important regions
which experiments can often confirm
Fig

28. Eukaryote polymerase binding and transcription initiation
are determined by cooperative interactions of
diverse proteins with diverse DNA sequences
Enhancer-binding factors
can be tissue-specific
Near DNA sequences: promoter-proximal elements
Distance-independent DNA sequences: enhancers/silencers
Fig

29. Drosophila dpp gene region contains many tissue-specific enhancers
Visceral mesoderm enhancer (VM)
Lateral mesoderm enhancer (LE)
Imaginal disk enhancer (ID)
Most tissue/cell-specific gene expression in eukaryotes
is controlled by enhancers
Fig

30. Chromosome rearrangements that create new physical relationships
among genes can result in
gain-of-function mutation
The In(3R)Tab mutation
brings into close proximity:
sr enhancer sequences
(drive thorax expression)
Abd-B gene
(product drives expression
of abdominal pigmentation)
+/ Tab/+
Fig

31. Chromatin structure influences gene expression
Euchromatin: rich in active genes
Heterochromatin:
Constitutive heterochromatin (e.g., centromere regions)
few active genes
Facultative heterochromatin: euchromatin in some cells,
heterochromatic in others
rich in genes; genes are transcriptionally silent
Epigenetic inheritance: inheritance of genes with same DNA
sequence, but different levels of expression

32. Mammalian X-chromosome heterochromatization
dosage compensation
inactivation of one X in female cells
(heterochromatic X is “Barr body”)
selection of X occurs in early embryo
(then is fixed for clonal populations)
mammalian females mosaically express
their X-linked genes
Fig

33. Imprinting: recently discovered in mammals DNA methylation usually
results in reduced levels
of gene expression
Differential methylation
of genes and transmission
of that methylation can
result in imprinting
phenomena
Fig

34. Prader-Willi syndrome can arise “de novo”
through a combination of mutation and imprinting
Fig

35. Position-effect variegation (PEV): relocation of euchromatic genes
to the vicinity of heterochromatin can result in mosaic inactivation
Clonal-determined heterochromatin spreading
Fig

36. Fig. 10-

37. Fig. 10-