Prokaryotic promoters Flashcards
How many promoter motifs with characterized consensus sequences are there?
5
How many promoter motifs does sigma recognize and bind to?
4
What are the 5 promoter motifs?
- -35
- -10
- Extended -10
- Discriminator sequence
- UP element
What promoter motifs does sigma bind to?
- -35
- -10
- Extended -10
- Discriminator sequence
How are nucleotides numbered?
The transcription start site is +1. Anything upstream is -1,-2, -3, etc. Anything downstream is +2, +3, +4, etc
What is the core promoter?
Everything within 37 bp of the +1 nucleotide
What is a housekeeping gene? How many promoter elements do they tend to have?
A gene that is needed for day to day functioning of the cell, so is transcribed all the time. Tend to have 4 to 5 promoter elements
What is a ‘strong’ promoter?
A promoter with high rates of transcription
What type of promoter motif do strong promoters tend to have?
The UP element, located at -40 to -60
How is the UP element different from the other promoter elements?
It contacts RNAP through the alpha subunit instead of sigma
What does the UP element do?
Increases the stability of the interaction between RNAP and the promoter, which increases the rate of transcription
What is a consensus sequence?
A specific conserved sequence at a particular location
What happens to the rate of transcription when the consensus sequence is mutated to resemble the ideal sequence less?
RNAP binding is reduced or abolished, so rate of transcription drops
What happens to the rate of transcription when the consensus sequence is mutated to resemble the ideal sequence more?
RNAP binding increases and is more stable, so the rate of transcription increases
What happens to the rate of transcription when there are indels in the promoter?
It disrupts the spacing of the consensus sequences, which reduces RNAP binding and the rate of transcription
