Regulation of gene expression - concepts Flashcards
Define constitutively expressed genes
continuously expressed ‘housekeeping genes’
Describe cis-acting elements
→ mutation found within the same gene that is being affected
Identify DNA/RNA sequences that affect gene regulation
Describe trans-acting factors
→ mutation in one gene may affect the expression of another
Typically protein (or RNA)
Identify factors that regulate expression of a target gene
Why are most genes regulated at a transcriptional level?
limits wasteful production of unrequired molecules
Protein coding transcripts tend to be more unstable (e.g mRNA) = quick turn over
Describe how trans-acting factors can activate transcription
Positive control: Trans-acting activators = cause activation
- Promote expression at weak promoters (have a weaker recruitment of RNAP)
Describe how trans-acting factors can repress transcription
Negative control: Trans-acting repressors = cause downregulation
- Interact with the alpha subunit of RNAP and promote DNA binding
Promoter sequence close to the consensus = ______ promoter
Promoter sequence close to the consensus = strong promoter
Promoter sequence further from the consensus = _____ promoter
Promoter sequence further from the consensus = weak promoter
Describe how the expression of enzyme coding genes can be regulated by substrate availability
Inducer → Substrates that mediate the upregulated expression of enzymes
Corepressors→ Products that mediate the downregulated expression of enzymes
Describe gene exp being regulated at the level of RNA processing
- Pre-mRNA splicing can occur in different patterns = from 1 mRNA transcript you can generate diff proteins
- There might be a productive / unproductive pathway
- The mRNA can be degraded, blocking expression
Describe how pre-mRNA splicing generates distinct mRNAs from a single transcript
One common form involves the inclusion of either one or other adjacent exon
Exon inclusion / exclusion is promoted by splicing activator or repressor proteins that bind to specific sequences in pre-mRNA
Describe how expression can be regulated at the level of translation, in prokaryotes
mRNA with a Shine-Dalgarno sequence shortly upstream of the initiation codon = promotes translation
- Could be influenced by proteins that bind to mRNA (translational-repressor) → block SD sequence and repress translation
- Small mols can bind to RNA and affect its structure → affects spacing between it and the SD sequence = translation repressed
- RNA structure influenced by physiological conditions → affects spacing between SD and start codon e.g some RNAs are not translated at low temps
Describe the autoregulation of gene expression
(negative feedback)
→ The gene product (protein) that is expressed can influence its own expression
When at high conc. = translation is decreased
At lower conc. = translation is increased
