L17 - Transcription Flashcards
(15 cards)
What molecule is chemically added to grow the mRNA?
Which end is it added to? What molecule is released during the process?
What type of metal ion is required for this chemical process? What amino
acids coordinate these ions?
Incoming NTP comes in where a phosphate and a base is added to grow the mRNA.
3’ end, pyrophosphate released.
3 Asp coordinating 2Mg 2+ ions
What are the names of the two sequences that define the start of a gene in E coli. (hint: their names are the same as their locations)
-10, -35
What are the roles of the three RNA polymerases in eukaryotes? Which one is responsible for
transcribing most mRNAs, and what is the main sequence that guides it to the promoter?
Rna Pol 1 - rRNA
Rna Pol 2 - mRNA, recognises TATAA box (at -30). 12 subunits, general transcription factors required for expression of almost all genes and gene regulator proteins (transcription factors) that regulate expression of a subset of genes.
Rna Pol 3 - tRNA, rRNA, other RNAs
True or False: RNA polymerase II is a large complex of many proteins
True
What is the difference between a general transcription factor and gene regulatory protein (transcription
factor)?
General transcription factor - required for expression of almost ALL genes (it is what we will be discussing in the lectures)
Gene regulatory protein - regulate expression of a subset of genes
What is TBP and what is its role during transcription?
TATAA box binding protein
What is TFIIB and what does it do? What is TFIIH and what is its role? What modification occurs to the CTD of RNA Pol II, and what does this achieve? What do termination factors achieve?
TFIIB binds to TBP and recruits Poll 2-TFIIF complex
TFIIH unwinds DNA at promoter (helicase activity); phosphorylates Pol 2 (within the CTD); recruits nucleotide-excision repair proteins
CTD (C-terminal Domain) of RNA Pol 2 is phosphorylated (switched on) during initiation so that Pol 2 can create RNA.
Termination factors leads to dissociation of mRNA
What three types of processing occur to the initial transcript to make a mature mRNA?
5’ cap, introns removed, poly A tail.
True or False? 7 methylguanosine is added to the 5’ end of an mRNA with a phosphodiester bond.
False, it is a 5’ to 5’ triphosphate bond.
What does the spliceosome do? Where in the pre‐mRNA are the sequences located that are recognised by this complex?
Removes introns from pre-mRNA
At the beginning (GU), middle (A) and at the end (AG). Leads to formation of loop (Lariat structure) where UG joins to A and then it is cut at the AG.
True or False: The process of splicing regularly introduces small variations between each mRNA.
True
True or False: The spliceosome contains both proteins and RNAs.
True, the subunits are called snRNPs and are made of both.
True or False: There is a sequence at the end of the mRNA that signals for a polyA tail to be added, but
this is not present in the original gene and has been added by the RNA polymerase.
False, a little bit is encoded by the gene and the other As are added by polyadenylate polymerase.
Where is the Cap-synthesizing enzyme for the 5’ cap bound?
To the CTD
Where is the splicesome found?
At the CTD
