4 - Transcription Flashcards
Transcription
Process of transcribing RNA by RNA polymerase using DNA as template
Antisense
Strand used as template
Sense
Coding strand (not used)
Direction of transcription
5’–>3’
Requirements for initiation of transcription
- RNA polymerase
- General transcription factors
- A TATA box or other initiation site
Steps of initiation of transcription
- TBP binds to TATA box and bends DNA
- TFII B binds and makes contact with both TBP and DNA
- A complex of TFII F and Pol II binds so Pol II is positioned over start site
- TFII E binds an forms docking site for TFII H
- TRII H binds as 2 subunits that have helicase activity
- TRII H unwinds DNA at start site
- Release of general TFs allows Pol to move down DNA and synthesis RNA
Combinatorial control
Eukaryotic genes are controlled by combinations of transcription factors binding to DNA binding sites in promoter
What is combinatorial control dependent on
- DNA sequences present
- Transcription factors present
- Interactions between regulatory proteins
How can transcription factors bound to DNA in regulatory regions influence transcription?
DNA/TF complex loops back to interact with the
TATA factors
Functional protein domains of regulatory proteins
- A domain that recognises the correct DNA promoter or enhancer element
- A domain that interacts with one or more proteins of the initiation complex
- A domain that interacts with TFs bound to their cis-element
- A domain that influences chromatin remodelling
- A domain that acts as a sensor of conditions within or outside the cell
Chromatin accessibility and histones
Modification of histone tails loosens their grip on the DNA (e.g. by acetylation, methylation, phosphorylation and chromatin remodelling proteins)
SWI-SNF
ATP dependent chromatin remodelling protein. Activates transcription by moving nucleosome away from TATA box allowing initiation complex to form
