RR2: Eukaryotic Transcription, an Overview Flashcards
what is the major regulator of gene expression?
transcriptional control
what is an overview of transcription? (the steps)
- DNA double helix locally denatures and one strand acts as template
- incoming ribonucleoside triphosphates (rNTPs) base pair with bases in the template DNA strand
- RNA polymerase sequentially joins the rNTPs from 5’ to 3’
- polymerization is energetically favored because the high energy bond between the alpha and beta phosphates is replaced by lower energy phosphodiester bond
RNA will look like the non template strand
what are the different areas on the related and transcription and the conventions of representation/naming?
nontemplate strand = coding strand
template strand = non coding strand
where the transcription starts is labelled as +1
upstream from that is the promoter region, which controls transcription
it can be very big and complex
then there is the coding sequence
before coding sequence and after where transcription starts is the 5’ untranslated region
after coding sequence is the 3’ untranslated region
what rate does RNA polymerase II move at?
1000-3000nt/min
what is the longest human gene and how long does it take to be transcribed?
DMD (dystrophin)
a whole day
what are the stages of transcription?
initiation:
polymerase, based on all the promoter information, has to decide where its going to transcribe
binds to the promoter sequence locally denatures DNA and catalyses the first phosphodiester linkage
elongation:
after intitiation
polymerase enters into processive state and continues to elongate RNA chain
polymerase advances 3’ –> 5’ down the template, denaturing DNA and polymerising RNA
termination:
polymerase recognises stop site, releases complete RNA and dissociates from DNA
how often does prokaryotic transcription change? and how is it regulated
responds to external stimulation
regulated by allosteric stimuli
what influences the rate of RNA synthesis in eukaryotes?
DNA binding proteins regulate it by enhancing or impeding RNA polymerase binding to promoter regions
sequences in the DNA proximal to the transcribed gene are critical for efficient transcription
how are different cells made different?
due to transcriptional regulation during embryogenesis
what is the difference between prokaryotic and eukaryotic mRNA?
prokaryotic mRNA is polycistronic, multiple proteins can be coded from the same RNA
eukaryotic mRNA is monocystronic
what are the similarities between eukaryotic and prokaryotic RNA polymerases?
all three hare common features, and then they evolved
all exist in multimeric complexes
some show significant similarity to bacterial subunits
most are essential
what is a special element present on the RNA polymerase II?
the CTD: carboxyterminal domain
repeats essential for viability, an unstructured region
what does the clamp in RNA polymerase do?
interacts with DNA
opens, and then closes over DNA and keeps it going
how can CTD be used to see regions of transcription (in polyetene)?
the CTD of RNA polymerase II is phosphorylated during transcription
phosphorylated CTD is red
un phosphorylated CTD is green
puffs show region of transcription
what are the sensitivities of the different polymerases to amanitin?
(1) Pol I is insensitive to
the toxin; (2) Pol II is highly sensitive; (3)
Pol III is moderately sensitive.
