Lecture 17 Flashcards
Initation
RNA pol binds to DNa
DNA unwound at the promoter
Very short chains are synthesized and released
Elongation
Polymerase synthesizes RNA
What is the elongation process also known as?
processivity
Necessary for elongation
core enzyme
Core enzyme
alpha 2, beta, beta prime, omega
Required for initiation of transcription
Holoenzyme
Holoenzyme
alpha 2, beta, beta prime, omega, sigma
What does the initial holoenzyme complex cover?
75 bp (-55 to +20)
Is the core enzyme or holoenzyme binding faster?
core enzyme is fast, but holoenzyme is more specific so it’s even faster
Sigma 70 promoters, amino acids, and preferred sequence
1000 promoters
613 amino acids
TTGACA to TATAAT
UP element
AT rich region located upstream of -35 box
expressed in highly expressed genes
-35 box alpha helix
4.2
-10 box
Pribnow box
TATAAT
Down mutation
decreases promoter efficiency and expressed at a lower level
cant bind as well
Up mutation
crank up expression
better binding
-35 mutations
affect inital binding
-10 mutations
affect melting rxn to open the complex
amino acids in 2.4 alpha helical region
arg, thr, gln, trp, tyr
What prevents sigma from binding DNA all the time?
sigma changes structure to expose binding sites when it attaches to the holoenzyme. DNA displaces the N-terminus when the complex forms.
Hairpin
intrastrand pairing (G-C rich) sequence located upstream of terminator sequence initates pause and release
Rho factor
extrinsic terminator
Process of rho factor
- Rho attaches to rut site
- Rho translocates
- RNA pol catches on hairpin and Rho catches up
- Rho unwinds DNA-RNA hybrid
- RNA released from DNA
Rut Site
rich in C poor in G
at the 3’ end of the RNA
Rho properties
hexamer
