1-44 Eukaryotic Transcription I Flashcards
(52 cards)
RNA polymerase 3 types and what they do
three types exist in eukaryotes
1. pol 1 (transcription of most ribosomal RNA’s)
- pol II (mRNA’s, mi, Inc,sn and snoRNA’s)
- pol 3 (tRNA’s, 5s r RNA ribososomal precursor, snoRNA’s, and other small RNAs)
why does Pol II pause?
regulatory step - Pol II is paused shortly after trancription begins.
pol II must be released from pause site in order for elongation to proceed
what do transcription factors do?
bind to enhancer sequences that can be far from the gene being transcribed. act by recruiting a mediator protein or chromatin modifier
what are enhancer sequences composed of?
DNA binding domain and an activation or repression domain (depending on if it up or down regulates transcription)
What do the parts of the enhancer sequences d?
DNA binding domain - provides specificity to its particular enhancer sequence
Activation/repression domain provides its up or down regulatory function
the DNA binding domain and activation/repression domains are both..
modular - meaning the binding domain can be combined with the activation/repression domain of another
if one domain is mutation
implications in cancer evolution?
example?
the other domain can function normally
-implications in cancer evolution. Mutations in either site can affect the action of the transcription factor to the point of causing disease
(actute lymphoblastic leukemia)
what are transcription mediators?
complex of proteins that bridges activatiors to RNA poly II and basal factors
required for transcription to begin
mediators are required for…
transcription to begin
chromatin modifiers are promising..
anticancer drugs
5’ capping
A 7-methylguanosine nucleotide is added to the 5’ end of the pre-mRNA. Helps to protect the mRNA from degradation, facilitate nuclear export, and allow translation by the ribosome.
3’-Polyadenylation
– Over one-hundred adenine nucleotides are added to the 3’ end of the pre-mRNA, past the poly (A) addition signal. Provides the benefits as the 5’-cap.
Splicing
pre-mRNA have introns spliced out leaving exons.
alternative splicing allows for more than 1 distinct protein to be transcribed from a single DNA sequecne
the end result of hormones?
hormones stimulate signal trasduction pathways leading to trasncription activation or repression
Rna polymerase uses what type of precursors?
ribonucleodies, not deoxyribonucleotides
RNA polymerases share many
basal factors
general initiation steps
- TBP portion of TFIID binds TATA box to bend DNA
- TBP and other general basal TF help recruit RNA poly 2 to promoter (forms pre-initiation complex)
- Pol II must be phosphorylated to leave promotor and start transcribing mRNA
antibiotic against trasncription?
Vancomycin. binds to DNA and blocks ability of Pol I and Pol II to elongate
Eurkaryotic RNA polymerases need basal TF factors to…
recognize promotor and form initiation ccomplex
what are enhancers and what do they do?
cis acting sequences located far away from gene in loops where TF interacts with complex called mediator.
Eukaryotic trasncription factors do what to stimulate RNA pol II?
bind enhancers
t-cell acute lymphocytic luekemia
caused by translocation of t-cell enhancer next to homeobox gene. This enahncer is evolved to be strong in T cells. So what happens is that now in t-cell you are making tons of hox11 protein. Way more than needed.
what determines the specificity of transcription factors?
TF’s fold up well and typically have alpha helix that inserts into DNA major groove. Side chains touch bases in base pairs, determins specificity in what genes they target.
big alpha helix in base groove touches base pairs, multiple contacts gives specificity
works without having to unwind DNA helix.
DNA site recognition is determined by?
amino acid-base pair interactions
