Transcription Factors in the

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Transcription Factors in the Central Nervous
System
Jau-Song Yu
Department of Cell and Molecular Biology Chang
Gung University
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THE TRANSCRIPTIONAL PROCESS Formation and
Regulation of the Transcriptional Complex
Cis-acting elements Trans-acting elements
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Gene expression as a biological amplifier
Gene mRNA Protein
Transcription 1000 X Amplication Trans
lation 100 X Amplication
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cDNA microarray analysis
Different genes
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Protein expression analysis by 2-D gel analysis
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Structure of transcription factors from different
families
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C2H2 zinc finger
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Helix-turn-helix Homeodomain
Leucine zipper
Helix-loop-helix
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Glucocorticoid and Mineralocorticoid Receptors
Are Transcription Factors
Nuclear receptors are ligand-activated gene
regulatory proteins
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Ligand-binding domain
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Glucocorticoid and Mineralocorticoid Receptors
Regulate Transcription in the CNS
Hypothalamic-Pituitary-Adrenal (HPA) systems in
rat
de Kloet et al. Endocrine Rev. 19(3)260-301
(1998)
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TABLE 2. Milestones in brain corticosteroid
receptor research
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Molecular mechanism of corticosteroid action on
gene expression
TF such as AP-1, NF-kB HRE hormone-responsive
element
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Gene-mediated steroid effects on membrane
properties
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cAMP Regulation of Transcription
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CREB transcription factor Transcription
factor that binds to the cAMP response element
(CRE) CRE palindromic sequence TGACGTCA in
the promoter region of a gene
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Identification of the DNA sequence that binds to
a specific DNA-binding protein
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Affinity-purification of a specific DNA-binding
protein
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CREB in rat hippocampal neurons
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Nature 1988 Aug 11334(6182)494-8 Phosphorylation
-induced binding and transcriptional efficacy of
nuclear factor CREB. Yamamoto KK, Gonzalez GA,
Biggs WH 3rd, Montminy MR. Clayton Foundation
Laboratories for Peptide Biology, Salk Institute,
La Jolla, California 92037. A nuclear protein,
CREB, has been isolated from rat brain and shown
to stimulate transcription of the cyclic
AMP-responsive gene somatostatin as a dimer.
Biochemical analysis suggests that dimerization
and transcriptional efficacy of CREB protein in
vitro are regulated by phosphorylation. These
findings demonstrate that cellular signals can
modulate gene expression by regulating the
covalent modification of pre-existing nuclear
factors.
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Dephosphorylation inactivation
(phosphatases?)
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CREM cAMP response element modulator (by
homology screens, PCR, interaction screening)
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CREB ---- dimers, leucine zippers and
DNA-binding domains
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Mechanism for generation of activators and
repressors of cAMP-stimulated transcription
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CREB and CREM play roles in many physiological
systems Memory and long-term potentiation
(Silva et al., Annu. Rev. Neurosci. 21,
127-148) Circadian rhythms (Foulkes et al.,
Trends Neurosci. 20, 487-492) Pituitary
function (Struthers et al., Nature 350,
622-624) Spermatogenesis (Sassone-Corsi P,
Sem. Cell Dev. Biol. 9, 475-482)
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The function of the CREB has been modeled in
transgenic organisms
Learning and memory stimulated by serotonin as
well as cAMP
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Drosophila as a model organism to study the role
of CREB in learning and memory
Fly (wt or mutants, obtained from wt fly fed with
ethylmethane sulfonate, EMS) trained
by odor avoidance learning Behaviorally tested
in an odorant-associated electric
shock Characterize mutants with learning and
memory deficiency dunce mutant deficient in
cAMP phosphodiesterase rutabaga mutant mutation
in adenylyl cyclase
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Odor Avoidance Learning
(one training cycle, 2.5 min total)
100 flies
100 flies
100 flies
100 flies
100 flies
Electrifiable copper grid
45 s
45 s
60 s
60 s
Fresh air
Fresh air
3-octanol (OCT) or 4-methylcyclohexanol
(MCH) (1o odor)
MCH or OCT (2o odor)
In a T maze
120 s for choice
n2
n1
OCT
MCH
n1 n2 50 50 for untrained flies
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Induction of a dominative CREB transgene
specifically blocks long-term memory in
Drosophila Yin et al., Cell 79, 49-58 (1994)
dCREB2 Drosophila CREB gene dCREB2a Activator
for CRE dCREB2b Repressor for
CRE dCREB2-mLZ Lost of Repressor function
2 leucine in LZ domain valine
(dCREB-mLZ)
HS-induced dCREB2b can be detected in brain cells
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Massed training cycle 10 consecutive cycle
without rest interval between them Spaced
training cycle 10 consecutive cycle with a
15 min rest period between each
wt flies 35 mM CXM, 12-14 hr (before
group) Training 35 mM CXM, 24 hr (after
group) Odor avoidance exp.
Performance Index (PI) 100 means 100 avoidance
of the shock-paired odor 0 means a
5050 distribution in the T maze
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Induction of the dCREB2-b transgene disrupts 1
day memory after spaced training, while 1 day
memory after massed training and learning are
normal
Can-S wt flies 17-2 and M11-1 hs-dCREB2-b
transgenic flies
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Induction of the mutant blocker (dCREB2-mLZ) does
not affect 1 day memory after spaced training
(dCREB2b)
(dCREB2-mLZ)
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hs-dCREB2-b induction does not affect olfactory
acuity or shock reactivity
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Induction of hs-dCREB2-b completely abolishes 7
day memory rentention
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(281-285)
The CREB and CREM transcription factors are
activated by phosphorylation of a key serine
residue by kinases stimulated by cyclic AMP,
Ca2, growth factors and stress signals.
Phosphorylation allows recruitment of CREB
binding protein (CBP), a large co-activator that
contacts the general transcriptional machinery.
Studies of the physiological roles played by CREB
and CREM have uncovered novel routes of
transcriptional activation. For example, in male
germ cells CREM is not phosphorylated but
associates with ACT, a member of the LIM-only
class of proteins that has intrinsic
transcriptional activity. Thus, in some
circumstances, CREM can bypass the classical
requirement for phosphorylation and association
with CBP.
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Conclusion CREB is an integrator of
intracellular homeostasis, while the
glucocorticoid receptor integrates whole-body
homeostasis