Lecture 5 - Transcription Flashcards
8/30/24
What allows for transcription elongation in bacteria?
RNA polymerase
How is transcription terminated in bacteria?
- RNA polymerase recognizes a stop codon
- RNA is released
What are the two transcription termination mechanisms in E.coli?
- factor-independent terminator
- rho-independent terminator
What is factor-independent termination?
releases the RNA after it makes a GC-rich stem-loop structure followed by a stretch of Uās
What is Rho-dependent terminator?
- Rho factor recognizes termination signal (rich in C residues and includes a Rut site)
- Rho binds to Rut site, RNA polymerase pauses at A-U rich region
- Rho travels towards 3ā end
- Rho releases RNA from RNA polymerase
What is Rho?
A homo-hexamer consisting of six identical subunits that has helicase activity
Is control of gene expression more complex in prokaryotes or eukaryotes?
eukaryotes
What is pre-mRNA?
it is the primary transcript before it is ready for export to the cytoplasm
What does transcription in eukaryotes and prokaryotes have in common?
- Initiation
- Elongation
- Termination
How is eukaryotic transcription different?
- exons/introns
- nucleus
- more proteins
What can you find from -25 to -30 in eukaryotes?
TATA box
What can you find from -75 to -80 in eukarotes?
CAAT box
How many RNA polymerases are found in eukaryotes
three
What is the function of polymerase I?
transcribes rRNA genes (excluding 5S rRNA)
What is the function of RNA polymerase II?
transcribes all protein-encoding genes and some snRNAs (Small Nuclear RNAs)
