Transcription / RNA Processing Flashcards
Number of RNA Polymerases in Eukaryotes
3
How are transcription and translation separated in eukaryotes only?
Transcription takes places in the nucleus while translation of mature mRNAs occurs in the cytoplasm.
Unspecific factors required for transcription initiation
General Transcription Factors (GTFs)
RNA polymerase responsible for transcribing large ribosomal rRNAs
RNA Polymerase I
Transcribes all mRNA, as well as microRNA precursors and most snRNA involved in splicing
RNA Polymerase II
Which RNA polymerase has polyadenylated transcripts?
RNA Pol II
What transcribes tRNA, U6 snRNA and the 5S rRNA gene
RNA Polymerase III
Location of the TATAA box
-25 to -30 upstream
What at -35 in a eukaryotic promoter recognizes TFIIB?
B Recognition Element (BRE)
What does TBP stand for in eukaryotic transcription?
TATAA Binding Protein
What is TAF in regards to eukaryotic transcription?
TBP Associated Factors
TFIID, a 15 protein complex, is made up of what?
TBP and TAFs
First step in eukaryotic transcription / binding of RNA Pol II?
TFIID binds the promoter
What happens after TFIID binds in eukaryotic transcription?
TFIIB binds to BRE (promotor) and TBP (part of TFIID)
What happens after TFIIB binds in eukaryotic transcription?
RNA Pol and TFIIF create a subcomplex. This complex binds the TBP-TFIID complex already in place.
What happens after TFIIF-RNAP binds the growing complex in eukaryotic transcription?
TFIIE and TFIIH bind the complex, completing the pre-initiation complex.
Which transcription initiation factor has helicase activity?
TFIIH
Which transcription initiation factor phosphorylates the c terminal domain of RNA Pol II?
TFIIH
What causes RNA Pol II to dissociate from the preinitiation complex and initiate transcription?
Phosphorylation of the 5th serine residue in a repeated amino acid sequence by TFIIH
What does the Carbon Terminal Domain (CTD) do in RNA Pol II after dissociating from the initiation complex?
Binds elongation and processing factors.
Role of “Mediator” in RNA Transcription
Interacts with GTFs, RNA Pol II, and gene specific factors
Which two RNA Poly III regions have downstream promoters?
5S rRNA and tRNA
Which RNA Poly III transcribed genes have upstream promoters?
U6 snRNA
Where does ribosomal RNA processing occur in eukaryotes?
Nucleolus
How many cleavages does pre-rRNA undergo during processing?
Two sets of cleavage
How are 5.8S and 28S rRNA bonded in processing?
hydrogen bonding
Which is non-coding – 5.8S or 28S rRNA
5.8S
In eukaryotic ribosomal RNA processing, what guides nucleases to the specific cleavage sites?
Small nucleolar RNA (snoRNA) and small ribonucleoparticles (snoRNPs)
Which enzyme processes the 5’ end of pre-tRNA?
RNAse P
RNAse P is active with its RNA portion without its protein portion necessarily. That makes it a what?
Ribozyme
What cleaves the 3’ end of a (pre)tRNA?
A conventional protein RNAse
What is added to the 3’ end of a tRNA?
CCA addition
Aminoacyl tRNA synthetase needs what to recognize the tRNA?
CCA addition
Modified version(s) of adenosine used in tRNA
Inosine
Four Aspects of Eukaryotic mRNA Processing
1) Capping
2) Tailing
3) Splicing
4) Editing
What is added to the 5’ end of pre mRNA?
7-methylguanosine cap
Which end of the pre mRNA is the 7-methylguanosine cap added to?
5’
What enzyme adds to the 3’ end of mRNA during processing?
poly-A polymerase
In mRNA polyadenylation, what sort of sequence is cleaved off downstream?
GU rich element
What is upstream from the polyadenylation cleavage site?
AAUAAA signal (10-30 bases)
First step in mRNA splicing?
Cleavage at the 5’ site (leaves a free 3’ end exon)
What happens to the 5’ end of an intron after cleavage?
Joins to a 2’ hydroxyl of an adenine base near end of intron. Forms a lariat
What is made up of 5 types of small nuclear RNA, other proteins, and is part of the spliceosome?
Small nuclear ribonuceloprotein particlar (snRNPs)
What structure creates looped domains similar in appearance to tRNA?
snRNPs
Which snRNP holds the first exon during splicing?
U5 snRNP
RNA Editing
Changing single bases to alter the amino acid sequence
What three things can trigger RNA degradation?
1) Lariats identified by the 2’-5’ phosphodiester bond
2) 3’ and 5’ naked ends are targeted
3) premature termination codons
What kind of proteins do mRNAs have a short half life for?
regulatory
What kind of proteins do mRNAs have a long half life for?
structural
What’s odd about RNA Polymerase III?
promoter can be downstream
Why is there a 7-methylguanosine cap?
prevents degradation by RNAse
