L15 Flashcards
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
