quiz 4 Flashcards
What is RNA pol complex?
pol 1, pol2, pol3
pol 2: made of 12 separate proteins that form core enzyme
-transcribes mRNA and other small RNAs
-like the apps that come w/ phone
-pol 1&3: transcription of rRNAs
-pol 3: transcription of tRNAs and other small RNAs
What is a promoter?
sequence of DNA in or near the coding sequence, to which the RNA polymerase complex binds
-first to be transcribed
-TATA box: where 2 DNA strands separated first -> A-T bond has 2H btwn it so easier to break
What are two different sequences that help bind to promoter?
-BREu: specific sequence of nucleotides upstream
-BREd: specific sequence of nucleotides downstream
What occurs at promoters?
initial bonding of RNA pol complex
What must happen for transcription to occur?
RNA pol complex must make sufficiently stable contact with promoter sequence
- variable interactions between regulatory DNA sequences and combinations of regulatory proteins
What does it mean for a gene to be off/on?
gene on: minimum stability of binding
gene off: less than minimum stability of binding
levels of transcription: levels of stability of binding
What is a transcription factor (TF)?
protein that binds to DNA and alters the likelihood of RNA polymerase binding to a promoter
-alters because it can increase OR decrease likelihood of binding to promoter
What is the basal transcription apparatus?
RNA polymerase complex and GTFs
(general transcription factors)
-minimum structure necessary to begin transcription
-particular proteins in big complex, their job is to bind to specific sequences -> serve as adaptors in giant complex
How many proteins comprise the basal transcription apparatus?
38 proteins!
26 GTFs and 12 RNA pol = 38!
What do we mean by basal transcription levels?
how can a cell cause the transcription level to be significantly greater than (or less than) basal values? YOU NEED MORE TFs
-repression and activation
-3 levels: activated, basal, repressed
How many TFs are encoded in the human genome?
1557
-one gene can have tens of TF binding sites
what is proximal promoter sequence?
there to activate or repress the transcription of the gene
-a way of increasing or decreasing transcription rate
Are there other regulatory sequences that govern gene-expression level?
enhancers
-at 250bp upstream, its no longer called proximal promoter, its called distal promoter
-will have more TF binding sites
What is an enhancer?
nucleotide sequence that is a binding site for activating TFs and that is usually located relatively farther away from the core promoter
-flexibility contributes to likelihood of being transcribed -> think rope at grand canyon
-stabilizes from top
-could be hundreds or hundreds of thousands of bp away
-could upstream, downstream, or inside a gene (introns)
How can enhancers contribute to more transcription?
the more proteins that help -> the more stable binding -> the greater the transcription levels
What is a co-activator?
protein that contributes to the activation level of a gene; transcriptional activators cannot bind to DNA by themselves
-can only bind to other proteins that bind to DNA -> middle men
What is the mediator complex?
multi protein (26 in mammals) complex
-stabilize the binding of basal transcriptional apparatus by binding to TFs
-another way to increase likelihood success to bind to promoter
What functions are served by proteins?
-enzymes
-antibodies
-antimicrobial peptides
-hormones
-receptors
-storage proteins
-structural proteins
-transporters
-genetic regulatory proteins
What levels of structure can be exhibited by proteins?
-primary structure
-secondary structure
-tertiary structure
-quaternary structure
What is primary structure?
order and identity of amino acids that make up a protein
-ex: actin will have different primary structure than hemoglobin
What is a secondary structure?
local spatial conformation of polypeptide backbone excluding the side chains
-ex: alpha helix, antiparallel beta pleated sheet, and parallel beta pleated sheet
-if you take away the coil of alpha helix, you take away function of that protein
