L15 Flashcards
(23 cards)
what is AP1
dimeric transcription factor composed of members of Jun and For families
what are June nd Fos
bZip factors
what do bZip factors do
dimerize through a leucine zipper motif and bind DNA through adjacent Basic region
why is the DNA binding subunit of LZ called basic region
because DNA binding domain has a lot of lysine and arginine, which are positively charged with lots of amine groups
can c-Jun form homodimers or heterodimers
both
can c-Fos form homodimers or heterodimers
only heterodimers
what controls c-Jun activity
phosphorylation/dephosphorylation
is c-Jun phosphorylated or not in unstimulated cells
phosphorylated on several set/thr residues in proximity of basic region
what happens when c-Jun is phosphorylatied
inhibition of DNA binding
why does phosphorylated c-Jun inhibit DNA binding
because the basic region is the region of DNA binding, and the phosphorylation is very close to it, so it interferes
is c-Jun phosphorylated or not in stimulated cells
ALSO YES - DIFFERENT SPOT
it’s phosphorylated in trans-activation domain
what molecule phosphorylates c-Jun
Erk and Jnk
what mediates phosphorylation near c-jun basic region
CKII and GSK3beta
what mediates phosphorylation in the activation domain of c-jun
JNK (and ERK)
this happens at docking domain
what are the 3 domains of c-jun
LLLL (Leucine wiper)
Trans-activation domain (TAD)
D (docking domain_
B (basic domain)
is c-jun -/- lethal
yes - embryonic lethal
what kind of mitogenic response gene is c-fos
‘early immediate gene’
undetectable in quiescent cells and then transiently and abruptly inducible in response to mitogenic stimulations
what is the most potent form of an AP-1 transcription factor
c-jun c-fos heterodimer
what consensus sequence does c-jun c-fos bind to
TGACTCA
what sorts of pathways does c-jun and c-fos regulate
cell cycle regulation, apoptosis, angiogenesis, metastasis
4 blocks of evidence that AP-1 plays a role in oncogenesis
- AP-1 activity is elevated in cells transformed by RTK and NRTK
- expression of a dominant negative mutant of c-Jun (designated TAM67) blocks transformation by v-src and activated Ha-Ras
- MEFs nullizygous for c-jun cant be transformed in vitro by v-src or Ha-Ras
- c-jun -/- MEFs with v-src or activated Ha-Ras gene form tutors in mice with long delay
AP-1 reason 1 AP-1 activity is elevated in cells transformed by RTK and NRTK
induced AP1 activity means this is downstream target
AP-1 reason 2: expression of dominant negative c-Jun
if you engineer TAM67 to have no D or TAD, it will now bind c-jun because it’s ineffective and inactivated
