Chapter 13 Flashcards
synthesis of the complete RNA molecule
elongation
responsible for promoter recognition
sigma subunit
transcription components of bacterial transcription
- RNA polymerase
- core enzyme
- sigma subunit
At the end of the gene, transcription terminates due to _ in the RNA.
hairpin formation
in some cases, (bacterial transcription) termination depends on the _
rho (p) termination factor
- occurs in the nucleus and is not coupled to translation
- requires chromatin remodeling.
Transcription in eukaryotes
Nuclear DNA is transcribed by three different RNA polymerases
RNA pol I, II, III
Transcribes all rRNA genes (except for the 5S rRNA)
RNA pol I
transcribes all structural genes thus all mRNA and some snRNA
RNA pol II
transcribes all tRNA genes and the 5S rRNA gene
RNA pol III
also influence transcription regulation in addition to promoters
enhancers
three features are found in most promoters
- Transcriptional start site
- TATA box
- Regulatory elements
- relatively short
- consists of the TATA box
- Important in determining the precise start point for transcription
core promoter
- cap and tail added
- introns exercised and exons spliced togther
RNA processing
a low level of transcription resulting from just the core promoter
basal transcription
- affect the binding of RNA polymerase to the promoter
- They are DNA sequences bound by transcription factors
- can be proximal or distal
Regulatory (or control) elements
inhibit transcription
silencers
DNA sequences that exert their effect only on nearby genes
- ex: tata box, enhancers, silencers
cis-acting elements
Regulatory proteins that bind to cis-acting DNA sequences
- ex: transcription factors
trans-acting elements
a core promoter element that binds the TATA-binding protein (TBP) of transcription factor TFIID and determines the start site of transcription
TATA box
required for all RNP II mediated transcription and help RNA polymerase II bind to the promoter and initiate transcription
General transcription factors
The primary transcript is heterogeneous nuclear RNA (hnRNA) that is posttranscriptionally processed by:
- Capping of the 5’ end
- Addition of a poly-A tail to the 3’ end
- Removal of the introns by splicing
capping enzyme of 5’ primary RNA transcript
methylated cap and triphosphate bridge
- addition of a short sequence or a tail of adenine (poly A-tail) nucleotides to the 3’ end of an mRNA molecule
- happens during RNA spilcing in eukaryotes.
polyadenylation
