Topic 5 Flashcards
regulatory proteins
either activate or repress transcriptional machinery
- bind to DNA
- interact w transcriptional machinery
- interact w other proteins
- chromatin domains (euk. only)
- physiological sensor domains
operon
a group of genes expressed together, usually as a polycistronic transcript
- prokaryotes ONLY
Positive control
needs an activator to turn on expression
-default is off
Negative control
needs a repressor to turn off expression
- default is on
- ie. lac operon
Inducible
an effector/inducer is needed to change expression (usually allosterically)
mirozygote
partial diploids
- E. coli carrying an F episome
episome
plasmid, extrachromosomal circular DNA
lacZ
beta-galactosidase coding gene
lacY
permease coding gene
lacA
transacetylase coding gene
palindromic
read the same backwards as forwards, usually bound by dimeric proteins
CAP
catabolite activator protein
cAMP
cyclic adenosine monophosphate
- activates lac operon when there is low glucose
araC
alone: binds to both O and I, sterically preventing transcription (REPRESSOR)
+ arabinose: binds only I, allowing transcription (ACTIVATOR)
polycistronic
multiple proteins are encoded on a single mRNA strand
biochemical pathways are usually ________ systems
negative
-repressor usually binds to operator when end product is present
attenuation
controls transcription prematurely by forming an intrinsic hairpin structure in response to a trigger (high trp levels)
Promoter-proximal elements
upstream promoter elements
- bind GTFs
- CCAAT box @ -100bp
- GC rich region @ -200bp
Distance-independent elements
silencers/enhancers
- up to 50kbp away from gene
- orientation independent
- use DNA looping to interact w RNA polymerase
SOX1
binding of enhancer in crystallin genes
enhancesome
large complex that acts synergistically to activate transcription
