chapter 30 RNA synthesis and processing Flashcards
the catalytic site of RNA polymerase contain how many metal ions? their functions and placement?
Which aminoacids interact with them
2 -metal ions
one of them remain tightly bound to the enzyme
One comes in and leaves with pyrophosphate
three aspartat amino acids
where do RNA-polymerisation reactions take place? and how many base pairs are they?
transcription bubble
17 base pairs
what are sense + and antisense - strands?
sense is the coding strand
while antisense is the template strand
Most newly synthesized RNA-chains have ….. at their ….end
pppG or pppA at 5’end
What forces the separation of RNA-DNA hybrid after the transcription is complete
A structure in RNA-polymerase
what mechanism is used by RNA-polymerases to correct errors? the error is
back-tracking, in in 10^4 to 10^5
which subunit in RNA-polymerase holoenzyme helps recognise the promoter sequences
sigma subunit. RNA-polymerase bind DNA but very weakly and until the sigma unit finds the proper promoter sites
what are the two common promoters found in bacteria
TTGACA (-35)
TATAAT (-10)
The region containing the two common motifs in RNA-transcription initiation is called?
core promoter
strong promoter and weak promoter
don’t have many substitutions => frequent transcription
many subsitutation => attenuated transcription
When is sigma unit released
is released when 9-10 nucleotides are produced
How many sigma factors does e.coli have
7
closed and open promoter complexes
how many basepairs
how is DNA distorted
double helical DNA
Separated DNA-strands
17 basepairs
by being wrapped around RNA-polymerase
What signals termination in RNA-transcription in bacteria
at which end
A palindromic sequence of GC-rich area + AT-rich followed by a series of U-residues
The RNA-DNA hybrid is unstable because of the hairpin that disociate from the polymerase and cause the polymerase to dissociate from the DNA.
3’ end
riboswitches
messenger RNAs senstive to certain metabolites.
High concentration of the metabolite => more stability of hairpin => Terminator structure is formed
what is of the function of rho-protein in bacteria?
how does it function
terminate RNA-transcription. Detects termination signals that are not recognised by RNA-polymerase alone. It is a DNA-RNA helicase.
Pursues RNA polymerase until it catches it in the transcription bubble. Hydrolyses ATP in the presence of single stranded RNA
What is the common feature of protein-dependent and protein independent termination in RNA-transcription
Termination signals lie in the synthesised RNA rather than the DNA-template.
name some antibiotics that can inhibit transcription
Rifampicin and actinomycin D.
the function of rifampicin
inhibit RNA-transcription in bacteria
specifically, the initiation of RNA-synthesis
by blocking the channel into which RNA-DNA hybrid must pass
function of actinomycin D in both eukaryotes and prokaryotes
binds to double helical DNA and prevents it separation through an intercalation by the phenoxazone ring.
what enzymes trim and modify the precursors of tRNA and rRNA
nucleases
the function of RNase P in e.coli
ribonuclease P generates the correct 5’ terminal of tRNAs
Ribonuclease III (RNase III)
excises 5s, 16s and 23s from primary transcripts by cleaving double-helical hairpin regions at specific sites
The RNA-polymerase CCA adding enzyme
Does not require A DNA-template
