eukaryotic polymerases Flashcards
what are the main steps of eukaryotic translation?
binding
initiation
elongation
termination
which part of transcription process does most regulation occur?
A binding
B initiation
C elongation
D termination
A and B
what is the mitch polymerase called? What does it do?
mRNAP or POLMRT able to transcribe 3 polycistronic transcripts
mRNAP polypeptide is encoded on chr 19
how does mRNAP relate to evolution?
as mitch derive from bacterial endosymbiosis, this single polypeptide is structurally similar to bacteriophages
what is the purpose of promoters?
cis-acting elements and help with orientation and binding of RNA polymerase
for transcriptional initiation
why does mRNAP require additional factors like TFAM, TEFM, MTERF?
need them to recognise the binding sites and hekps with transitions of differennt steps of transcription
how do the accessory factors for mRNAP help with transcription?
> structurally
when transcription elongation complex forms, the a-factors convert mRNAP into a processive polymerase
able to continously carry out DNA synthesis without pausing/frequent dissociation from template
what is the function of terminator sequence?
allows RNAP to stop transcribing and dissociate from DNA and release RNA transcript
= transcription is terminated
what are the main differences between euk mRNAP and nuclearRNAP?
nRNAP employ 100 a-factors whilst mRNAP use 4
nRNAP transcribes 22,000 transcripts, mRNAP does 3 transcripts
what is a unique feature of RNAP-2? What is its purpose?
has a reversibly phosphorylated CTD. Unphosphorylated, able to be recognised by general TF
phosphorylated by TFIIH allowing GTF to dissociate and elongation factors bind = TEC formation
also binding of termination factors
where does transcription take place in euk and pro
pro - in the nucleus alongside translation
euk - in the nucleus alonqgside the rna processing
what is a feature of RNAPII promoters?
if it is a housekeeping gene, often promoter contain a CpG island
also promoters are highly variable and diverse with many motifs, not just TATA box
what do the 3 RNAP nuclear trancribe?
RNAP1 = rRNA
RNAP2 = mRNA
RNAP3 = tRNA
how does the mechanism of transcription using RNAP-3 differ from usual?
because of its small size, no need for elongation factors and also able to terminate too
> RNAP-3 is self sufficient and
doesn’t require accessory factors
how does RNA polymerase move along the DNA?
by scrunching, inchworming or transient excursions (move and pause)
what are enhancers?
they are long-range regulatory elements found upstream of the TRANSCRIPTION START SITE
able to recruit mediator complex which activates and finetunes transcription, aids helicase and kinase activity of TFIIH and K
what are the different classes of TF structure?
helix -turn helix
zinc finger
basic leucine zipper
basic helix turn helix
how does histone and dna interact?
histone is 147bp protein made up of H1 linker, h2a, H2b H3, H4 OCTAMER
dna will wrap around histone 1.7 times and helps to stabilise and package DNA as histones are postively charged aa and dna phosphates are neg-
what is the functions of chromatin remodelling complex?
MULTIPROTEIN COMPLEX that can modify histones by sliding or detaching// uses protein binding to create nucleosome free zones or even encourage nucelosome formation
or can post-transcriptionally modify histone tails
> basis of epigentic
