Transcription Initiation in Eukaryotes Flashcards
What is the other name for RNA polymerase
Holenzyme
After initiation what happens to the closed complex
Forms a open complex which goes on to be elongated
what are promoters
cis acting DNA regulatory element through which transcription is initiated and controlled
At what position are the consensus sequences
-35 to -10
what are the four core (basal) promoter elements
TATA box, Initiator (Inr), DPE and BRE
at what position is the TATA box located
-31 to -26
at what position is the Initiator (Inr) located
-2 to +4
what % of protein coding genes in mammals lack an obvious TATA & Inr
60-70%
how does transcription initiation occur
at a lower rate
at several start sites
start sites are associated with regions with a high frequency of -
CG sequences - CpG islands
most C residues are followed by G are
methylated
generally C residues in CpG islands -
escaped methylation (hypomethylated)
What is the effect of methylation of CpG islands
silencing
UAS & enhancers =
activator binding sites
URS & silencer =
repressor binding sites
how does sequence comparison identify promoter elements
identification of the TATA box
examples of reporter genes are
GFP, luciferase, LacZ (B-glactosidase)
what are the target genes and location
mRNA and Nucleus
what is the structure of bacterial RNA polymerase
ß subunit
ß’ subunit
α subunit (x2)
ω subunit
how many subunits are in yeast RNA polymerase II
12
what are general transcription factors (GTF’s)
In eukaryotes, there are sigma factors which are RNA pol specific.
where does GTF form a complex, and what does it do
on TATA box, recruits RNA pol II to the promoter and direct initiation at start site
how many GTFs and name them
6 - TFIIA,B,D,E,F,H
the helicase activity of which TFII seperates the template strand at the start site
TFIIH
