Transcription In Eukaryotes Flashcards
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3 similarities between transcription in prokaryotes and eukaryotes
- Both require DNA template
- RNA polymerase responsible for transcription in both
- Informtaion from DNA copied onto RNA
Where is the TATAA box located
-25 region and -75 region is CAAT box
Where is RNAP 1 located and what is its function
Located in the nucleolus
Responsible for rRNA transcription, processing and assembly
Synthesizes all rRNA molecules except 5S rRNA molecule
RNAP II location and function
Nucleus and sysnyhesises protein coding RNA. mRNA
Transcribing majority of eukaryotic Gene’s
And also genes for several regulatory RNAs , microRNAs and long coding RNAs
RNAP III location and function?
Nucleus
5S pre rRNA
Pre tRNA
small nuclear pre RNAs(responsible for spilling and regulation transcription factors)
What is the transcription pre initiation complex?
Refers to the complete assembly of transcription factors and RNA polymerase bound to the promoter region
TFIID binds to prompter region first. Why?
Presence of tata binding protein subunit which binds to to the tata box along with TFIID
After TFIID binds, which other 5 transcription factors bind and in what order
TFIIB, TFIIE, TFIIH, TFIIA, TFIIF(comes along with RNAP II)
How many protein subunits has RNAP II
12
Transcription bubble consists of about how many bp
25
Distinguish between introns and exons
Introns are the non coding regions of genes and exons are the coding regions of genes
Why is freshly formed mrna called pre mRNA.
Because processing is yet to occur
What is processing?
Removing introns and joining exons together
There are structures added to the ends of the mRNA. What are they
Polyadenyl tail in a process called polyadenylation to the 3’ end and Guanine cap to the 5’ end
When does polyadenylation begin
Begins as the gene terminates
How is transcription terminated in RNAP 1
the rRNA genes transcribed contain a sequence of specific 11 BP which are recognized by Transcription Termination Factor 1. Binds the DNA at that sequence preventing further transcription and causing RNA and RNAP1 to disengage
How is transcription terminated in RNAP II
Genes Lacks specific sequence that direct RNAP II to terminate at specific places
Can transcribe up to 1000 bp past actual end of gene
Transcript cleaver at internal site before RNAP II finishes transcribing
Releases upstream portion of mRNA
Remainder of transcript is digested by a 5’ exonuclease (Xrn2) in humans while transcription still taking place
Exonuclease catches up with RNAP by digesting overhanging RNA and helps disengage RNAP II
READ SLIDE 28 AND 29
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Why are death cap mushrooms deadly
They produce a toxin, amanitin which inhibits RNAP II
What is Rifampicin
It is an antibiotic which inhibits RNAP in bacteria
Poly A tail function?
Makes RNA more stable and prevents its degradation
Additionally, the poly-A tail allows the mature messenger RNA molecule to be exported from thenucleusand translated into aproteinbyribosomesin thecytoplasm.
Which enzyme is responsible for the addition of the 3’ poly A signal
The Poly(A) polymerase enzyme
What is the function of the G cap
The 5’ cap is added to the first nucleotide in the transcript during transcription. The cap is a modified guanine (G) nucleotide, and it protects the transcript from being broken down. It also helps the ribosome attach to the mRNA and start reading it to make aprotein.
Enhancer?
Anenhanceris a DNA sequence that promotestranscription.
