TMC 9 Flashcards
What is the function of RNA Pol I?
Transcribes the 45S rRNA precursor gene which is processed into the 18S rRNA, the 5.8S rRNA and 28S rRNA
What is the function of RNA Pol II?
Transcribes the protein encoding genes in eukaryotes and many non-coding RNA genes
What is the function of RNA Pol III?
Transcribes the 5S rRNA, tRNAs and other small RNAs
Describe the core promoter in eukaryotes.
40 to 70 bps upstream
TATA element ~25bp upstream
Recognition element(BRE) called TFIIB
Initiator element
Downstream promoter element
What are transcription factors?
Proteins that bind to regions upstream of the gene to promote transcription
Work tor recruit RNA pol II in order to initiate RNA transcription
Can have a DNA binding domain or an activation domain or both
What is the difference between General transcription factors and specific transcription factors?
GTFs bind to the core promoter region while STFs binds to the upstream promoter region and are usually regulated
What is the difference between TFIID and TBP?
TFIID is a GTF with 12 subunits and TBP is one of its subunits that binds to the TATA box in the core promoter region to initiate transcription.
TBP is called the TATA binding protein. TBP is a central TF.
What is meant by basal transcription?
The transcription that occurs when RNA pol II, GTFs, core promoter DNA and NTPs are added together
What are UPEs?
Upstream promoter elements - DNA sequences upstream from the core promoter to which specific transcription factors bind
What are enhancers?
DNA elements that reside upstream or downstream of many genes they can work a long distance away from a promoter in ether orientation
With respect to gene regulation in eukaryotic cells, explain the differences
between the core promoter, UPEs and enhancers.
What is the basal transcription complex?
The complex of GTFs and other factors built up in the core promoter region
Outline the different ways that a TF can activate transcription
Activating domain interacts directly with proteins in the basal transcription complex and activates/stimulates transcription
Co-activators which interact directly with factors in the basal transcription complex and activate transcription
Some bind closed chromatin and initiating alterations that open chromatin up into a 10nm fibre so other TFs can bind and establish a transcription complex
List all the proteins that you might find in a transcription initiation complex.
GTFs
STFs
Regulated STFs
Enhancer binding proteins
Mediator
List and explain 5 ways that transcription factors can be regulated
(In)activation of the TF by addition/subtraction of a small chemical group or ligand
Dependency on homodimerisation/heterodimerisation for activity - TFs have to reach a certain concentration before homo or heterodimers can form
Proteolytic cleavage - TFs are made in an inactive precursor format and must by cleaved by a protease in order to become active
TFs kept in cytoplasm to prevent them from binding to target sites on DNA - may be translocated into nucleus to be active which is regulated by modification or binding of TF to other protein
TF is kept inactive by repressor hitherto when the repressor is removed
