11. Transcription 2 Flashcards
how was the RNA polymerase’s strucuture determined (its using an experiment)
using ion exchange chromotography
what did ion exchange chromotography do to determine how
three steps (what was added and what did it do)
the collumn contatins phosophocelluose (anionic)
proteins bound to RNA pol are positive therefore make ionic bonds
NaCl was added to elute the protein. higher con salt required if more ionic bonds were made with phosphocelluose and proteins
is the protein concentration of RNA polymerase higher in a DNA strand with nicks and broken ends or a DNA strand without nicks and broken ends?
why?
its higher in DNA strands with nicks and broken strands because transcription needs a template which is broken to begin transcription
what are the four proteins bound to RNA called?
alpha, beta, beta prime and sigma
α , β , β’ , σ
what RNA polymerase called without sigma?
core polymerase
whats RNA polymerase called with sigma binded?
the holo enzyme
what are the transcription rates on a
DNA with nicks with RNA polymerase that has sigma attached
DNA without nicks and with sigma attached
DNA with nicks with RNA polymerase that has sigma not attached
DNA without nicks and with sigma not attached
calf thymus.- broken ends
T4 - no nicks
what is the function of sigma on RNA polymerase?
it helps RNA polymerase locate promoters
when RNA subunit binds the DNA template?
the beta prime subunit, B’
which RNA pol subunit binds regulatory sequences?
the alpha subunit, a
theres two of these
which RNA pol subunit forms phosphodiester bonds?
the beta subunit, B
which RNA pol subunit recognises promoter sequences and allows initiation of RNA synthesis
the sigma subunit, σ
what is the closed promoter complex?
the RNA polymerase as the holo enzyme has the sigma subunit binded weakly to the DNA. Its searching for a promoter
when the RNA polymerase finds a promoter sequence, it binds tightly to become the closed promoter complex
what are the two steps that occur after the RNA is in its closed promoter complex (found the promoter sequence)
explain what happens here
1. open promoter complex - localised melting of the DNA occurs to unwind the DNA around the inititiation site.
2. initiation of transcription, mRNA is synthesised
how does RNA polymerase bind to DNA? think about the bonding
there are specific interaction with H bond acceptors and donors which interact with the amino acids on the proteins structue of RNA polymerase
when does sigma leave RNA polymerase?
after RNA polymerase has bound and intitated transcription, the first few nucleotides have been transcribed and the promoter sequence is now behind the polyerase, sigma skiddadles
which direction does rna polymerase travel in?
RNA polymerase travels in the 5’-3’ direction
starting at 5’ and going towards 3’
what is the roles of the CTD A subunit? (theres also the NTD A subunit)
how does it do this?
the CTD alpha subunit is and enhancer which makes it ranscription stronger and increase the likelyhood of a sucessful transcription.
it sits upstream to stabilise transcription
