Transcription Flashcards
(14 cards)
Which subunit of prokaryotic RNA-Polymerase helps it bind promoter sequences tightly?
Sigma factor
What is an RNA Polymerase core enzyme, associated with its sigma factor called
RNA Polymerase Holoenzyme
What is described by the process of abortive initiation?
Initially, the polymerase holoenzyme pulls DNA into its active site, rather than sliding along it, thus expanding the transcription bubble. RNA synthesized that way is quickly discarded to relieve the considerable amount of stress created by this “scrunching” mechanism. This process repeats for a certain time. At some point, however, abortive initiation is completed and elongation follows. The stress generated in the process of abortive initiation helps the polymerase holoenzyme break free from the promoter region and dissociate from its sigma factor to begin sliding along the DNA and thus properly transcribing the entire gene.
How do termination signals end the elongation process?
If a termination sequence is transcribed into RNA, it folds into a hairpin structure that facilitates the entire transcript’s release from the RNA polymerase.
What is a consensus nucleotide sequence?
A summary or “average” of large amounts of analogous nucleotide sequences derived from comparison.
Which is a common sequence that signals the start of transcription in eukaryotes?
TATA-Box
How are the general transcription factor responsible for TATA-Box binding and its subunit responsible for TATA-Box recognition called?
TFIID and TBP (TATA-Box Binding Protein)
Why is TFIID crucial for assembly of other general transcription factors?
By binding the TATA-Box, it causes a large distortion in its DNA. This way both sides of the distortion are brought into closer proximity, allowing for subsequent protein assembly and eventual formation of the transcription initiation complex. *also applies to other sequences near transcription start point
Which role(s) does TFIIB play in the formation of the transcription initiation complex?
Recognition of BRE element (sequence near TATA Box), positioning RNA Polymerase accurately at the start of a transcription site
Which role(s) does TFIIA play in the formation of the transcription initiation complex?
Not always required, stabilizes binding of TFIID
Which role(s) does TFIIF play in the formation of the transcription initiation complex?
Stabilizing RNA Polymerase interaction with TFIIB, helps attracting TFIIH and TFIIE
Which role(s) does TFIIE play in the formation of the transcription initiation complex?
Attraction and regulation of TFIIH
Which role(s) does TFIIH play in the formation of the transcription initiation complex?
Unwinds DNA at the transcription start point, phosphorylates Ser5 of the RNA polymerase C-terminal domain (CTD); releases RNA polymerase from the promoter
Which functions does the phosphorylation of the CTD of an RNA Polymerase serve?
Release from transcription initiation complex, recruiting parts of the RNA-processing machinery
