RNA transcription Flashcards
Which bacterial RNA is most abundant?
rRNA, about 80%
How big is tRNA?
4S, about 75 base pairs
Which RNA types are only found in eukaryotes?
miRNA and snRNA
What is the core enzyme of bacterial RNA?
ɑ2ββ’
Which bacterial RNA polymerase subunit recognizes the promoter?
σ
Which subunit contains the catalytic site?
β
Which subunit binds the DNA template?
β’
What is the role of the ɑ subunit of bacterial RNA polymerase?
Structural, may interact with regulatory proteins
Which DNA strand has the same sequence as mRNA?
sense
Which strand contains the promoter region?
sense
What are the two elements of the prokaryotic promoter region?
-35 region and the -10 Pribnow sequence
What is required for the sigma subunit’s DNA binding domain to be unmasked?
Must be bound to core RNA polymerase
What is the first base transcribed?
purine triphosphate
How long is the DNA-RNA hybrid during transcription elongation?
8 bp
What sequence is necessary for rho independent transcription termination?
GC rich palindrome followed by UUUs
What is the target of rifampicin?
It targets the beta subunit of bacterial RNA polymerase and inhibits the formation of the first phosphodiester bond.
What is the structure and function of rho?
Hexameric helicase ATPase which terminates transcription by unwinding the RNA from DNA
What type of drug is actinomycin A? What does it inhibit?
Intercalating agent which inhibits transcription and elongation by RNA polymerase. Not specific to prokaryotes or eukaryotes.
Which RNA polymerase transcribes mRNA in eukaryotes?
RNA pol II
Which subunit does eukaryotic polymerase lack?
Sigma
What type of interactions govern transcription initiation?
polymerase-protein interactions
What do inducible elements dictate?
Specificity of transcription
What do constitutive elements regulate?
Rate of transcription
What do basal elements provide?
Initiation site for transcription
Which DNA sequence is found in the basal element?
TATA box
How do enhancers affect transcription?
Can bind activators or repressors. Activators interact with TAF to enhance rate of transcription
In what order do proteins form the Pol II pre-initiation complex.
Binding of TBP recruits TAFs and transcription factors IIA through IIH. Then polymerase II binds and the C-terminal domain of the large subunit is phosphorylated by TFIIH. which releases enzyme from the initiation site.
What is the transcription complex which carries out elongation?
TFIIF and Pol II
Why does transcription by Pol I and Pol III lack an elaborate control scheme?
The rRNAs (pol I) and tRNAs (Pol III) are needed in large amounts almost all the time.
Split promoter
Promoter for Pol I transcription initiation with binding sites for upstream binding factor (UBF) and core binding factor (CBF).
Internal promoter
Promoter for genes transcribed by Pol III located at +55 to +80. Binding of TFIIIA, B and C permits association of Pol III.
α-amanitin
Preferentially inhibits RNA pol II, and to a lesser extend Pol III. Does not inhibit Pol I.
Which type of RNA would be most transcribed in a cell poisoned with α-amanitin?
rRNA
