cellular signal transduction 2) from the membrane to the … · 2016-10-19 · cellular signal...
TRANSCRIPT
CELLULAR SIGNAL TRANSDUCTION 2) From the membrane to the nucleus
Part F
TRANSCRIPTION FACTORS AND THE
REGULATION OF TRANSCRIPTION
Rainer deMartin / Erhard Hofer Institute of Vascular Biology and Thrombosis Research
Vienna Competence Center Lazarettgasse 19, 1090 Wien
Rainer deMartin: Principals of transcriptional regulation Structural features of transcription factors Basic mechanisms of transcriptional regulation Erhard Hofer Activation of transcription factors by surface receptors: Summary selected examples discussed in part B: CREB, SRF, NFAT, SMAD Some additional specific example: Regulation of signaling pathways/transcription factors by proteolytic cleavage: WNT, NOTCH (embryonic development, adult stem cells) Nuclear import of transcription factors Chromatin and transcription Transcription initiation complexes
SMAD
SMAD/Co-SMAD
SMAD
STAT STAT A-Cyclase PLC Ras
STAT
cAMP
Signaling pathways: Receptor to transcription factors
PKA
SRF
IKKK
NFAT / NFκB
CREB, SRF, NFAT, SMAD
Gene regulation by PKA:
CREB bound to CRE is phosphorylated by PKA, activates transcription without effect on DNA binding
Example 3
Gene regulation via MAPK pathway (activated by Ras or PLC-γ/PKC): The phosphorylated MAPK ERK is transported into the nucleus and phosphorylates the transcription factor TCF on the promoter
ERK: extracellular signal regulated kinase TCF: ternary complex factor SRF: serum response factor SRE: serum response element (DNA binding sequence for TCF and SRF in promoter of various genes)
Genes for Cell cycle/ Proliferation early response genes, e.g. c-fos
or: PLC-γ Raf MEK
Ca++
Calmodulin
Calcineurin
NFAT
P I
Gene regulation via Ca++ Signaling pathway - the Phosphatase Calcineurin dephosphorylates NFAT NFAT translocates into nucleus NFAT= transcription factor (nuclear factor activated T cell) Kern
P
Gene regulation via TGF-β-R / SMADs: Transport of phosphorylated SMADs into nucleus
Regulation of transcription factors
by proteolytic cleavage
WNT signaling pathway Secreted signaling peptide, important in embryonic development, mutatios on proteins of wnt signaling pathway frequent in cancer
Example 4a
Wnt Wingless (Drosophila) Int-1 (breast cancer oncogen) (detected experimentally by virus Integration) In signalling pathway: APC (adenomoteous polyposis coli protein) mutated in adenoma of colon and 80 % of colon cancer induces myc gene and proliferation
(LDL rceptor related protein)
(Signaling protein)
(Corepressor)
β-Catenin signaling pathway: w/o signal: β-catenin is continously phosphorylated, ubiquitinylated, degraded in proteasom Wnt-signal: Kinase is inhibited, non-phosphorylated β-Catenin transported into nucleus, activates transcription by competing with a corepressor
(β-Catenin Coaktivator)
Phosphorylation, Ubiquitinylation, degradation in proteasom
components of the WNT signaling pathways e.g. important for maintaining the stem cell population in gastro-intestinal tract, over-activation by APC mutation – leads to colorectal cancer
Notch hedgehog
1- Embryonic development e.g. nerve cells Drosophila, Delta on nerve cells signals to neighbouring cell: do not differentiate to nerve cell, peptide translocates into nucleus and converts CSL to become an activator 2- Angiogenesis: Tip versus stalk cell, tip cell signals stalk cell not to become another tip cell
Example 4b
Nuclear import / -export
Nuclear membrane: Double membrane with nuclear pores
26 nm
Nuclear pore complex
innere Seite
The nuclear localization signal is a basic amino acid sequence
Model of nuclear import mediated by the small G-protein Ran
Model of nuclear import and export
CHROMATIN
Summary of chromatin structure
Interphase
Metaphase
Eigenschaften von Insulatorelementen
model
Change of chromatin structure by activator protein
Ac
Ac
HAT
HDAC
condensed CHROMATIN no TRANScRIPTION Z.B. HETEROCHROMATIN
loose CHROMATIN TRANCRIPTION Z.B. EUCHROMATIN
HAT = HISTONACETYLTRANSFERASE ACTIVATOR OF TRANSCRIPTION HDAC = HISTONDEACETYLASE REPRESSOR of TRANSCRIPTION
DNA
NUCLEOSOM
CHROMATIN
GENEXCS18
A
REPRESSION
ACTIVIERUNG
HDAC
X
Y
HAT
Target GENE
Target GENE
Z
REGULATION OF TRANSCRIPTION BY CHANGE OF CHROMATIN STRUCTUR
condensed Chromatin
open Chromatin
Repressor
Aktivator
GENEXCS19
Gene regulatory proteins form frequently large
complexes
DNA Looping
Mediator
Gene expression