Transcription Flashcards
(22 cards)
In which direction is RNA transcribed? And the DNA strand read?
RNA transcribed 5’ to 3’
DNA read 3’ to 5’
The transcript created has the same sense as which strand? sense/non-sense
sense (non-template)
Sigma factor
~ locates the transcriptional start site by recognising the promoter
~ interacts with DNA via several domains
~ bacteria
Holoenzyme
a biochemically active compound formed by the combination of an enzyme with a coenzyme
RNA pol I
~ eukaryotes
~ rRNA
~ found in nuclelous
RNA pol II
~ eukaryotes
~ mRNA, snRNA, miRNA
~ found in nucleoplasm
RNA pol III
~ eukaryotes
~ rRNA, tRNA, snRNA
~ found in nucleoplasm
snRNA
small nuclear RNAs found in spliceosomes
miRNA
regulate gene expression
Core promoter elements
direct the binding of the transcription initiation complex
TBP
TATA-binding protein
~ when it binds to TATA box it promotes the binding of TFIIB to the BRE sequence
BRE
TFIIB recognition element
Which RNA pols is TBP important for?
I, II and III
Promoter clearance
displacement of the protein loop helps polymerase to break away from the promoter
Comepare the functions of DNA gyrase and DNA topoisomerase I in E.coli.
~ DNA gyrase removes positive supercoils ahead
~ DNA topoisomerase I removes negative supercoils behind
Histone chaperones
remove nucleosomes ahead of RNA polymerase and reassembles them behind it
e.g. FACT, Asf1, Spt6
~ EUKRYOTES
RNA polymerase can stall because of…
~ a mis-inserted nucleotide
~ changes in supercoiling, the tension must be relieved
Type I terminator
a.k.a. Rho-independant or Intrinsic terminators
~ no additional factors required for termination
~ in E.coli
Type II terminators
a.k.a. Rho-dependent terminators
~ Rho factor is required for termination (requires ATP)
~ in E.coli
Allosteric model of termination
RNA pol II continues to transcribe after the polyadenylation signal but the mRNA is cleaved at the poly(A) signal and the 3’ end of the mRNA is processed
Torpedo model of termination
after cleavage at the poly(A) site, anything downstream of it is digested by Rat1 (5’ to 3’ endonuclease)
Abortive initiation
the release of short RNAs by RNA pol after it fails to make full length RNA on its first attempt
