GTS351 Theme 4 summary

The Process of Transcription

Eukaryotic transcription
- Is the synthesis of RNA molecules copied from a DNA template
- Carried out in the nucleus
- Is the major level at which genes are regulated




Stages of transcription
- Transcription initiation
- Requires open chromatin structure at the promoter region -
allows access to regulatory molecules
- Transcription factors locate and bind to short DNA control
regions in the promoter of genes
- General TFs recruit RNA pol to the promoter
- Additional activator/repressor proteins determine the level of
transcription
- Transcription elongation
- Termination of transcription

, Transcription initiation
- RNA pol II requires that general transcription factors assemble at the
promoter
- TFIIA, TFIIB etc
- General transcription factors are those that occur at every locus
- Initiation occurs at the TATA box which is 30 bp upstream of the +1 start
site
- TATA is first recognised and bound by TFIID and specifically by the TATA
binding protein subunit TBD of TFIID
- Binding of TFIID causes a dramatic distortion in the DNA of the TATA
box
- Other TFs bind to the complex in order along with RNA pol to form a
basal transcription complex
- BTC also called pre-initiation complex (PIC)
- Takes place in “transcription factories” - loops of chromatin containing
genes to be transcribed move out to foci with RNA pol II

Forming a basal complex
- TFIID complex binds to TATA via its TBD subunit - is a protein-DNA
interaction
- TFIIA then binds to TFIID and helps stabilise TBD-DNA interaction
- TFIIB recognises TFIIDA-DNA complex and binds on opposite sides of
the DNA at sequences called BREs
- TFIIB recruits RNA pol II that is in association with TFIIF
- TFIIB also helps position RNA pol II
- TFIIE and TFIIH then bind
- TFIIH has kinase activity - phosphorylates the C-terminal repeat domain
(CTD) of RNA pol II