5 Transcription Flashcards
what direction is RNA synthed in?
5-3
what links nucleotides in RNA?
5-3 phosphodiester bonds
What pol synth RNA?
DNA dep RNA pol needs 3’ OH and read 3-5 but synths 5-3
what are the components of prok RNA pol?
alpha/beta 4 unit core and single sigma factor
what is the function of the sigma factor
scans for pribnow boxes to initiate transcription
what does RNA pol I make?
rRNA w/o 5S
what does RNA pol II make?
mRNA
<p>
| what does RNA pol III make?</p>
<p>
| tRNA, sRNA like 5S</p>
how does the DNA and RNA sequences relate after transcription?
RNA is complementary to template strand and identical with T->U swap as the coding DNA strand
what are the RNA comparisons in terms of maturity before translation between euks and proks?
prok RNA are made from polycis genes so they have all components that are needed for a given function, they are dumped into the cyto, they do not have post tran mods.
Euk transcription is in nuc, has introns removed and exons spliced, has methyl cap and poly a tail added before exiting nuc
how does poly know which sequences it needs to transcribe?
it looks for non coding promoter regions
how does DNA promotor elements compare between euk and prok?
prok has TTGACA at -35 and pribnow at -10
euks have random upstream enhancers as well as promoter elements along with CAAT/GC regions at -40-(-100) and TATA at -25
what is the RNA tran complex for euks consist of?
TFIIA and cofactors bind to TFIID(aka TBP) which looks for TATA box, TBP also is bound to TFIIBFEH which holds RNA pol
How does coactivators work?
coactivators(tran) search for enhancer sequences(cis) away from coding sequence which increase rate of transcription while repressors(trans) silencers(cis) will decrease transcription rate
what class of receptors can bind directly to DNA
steroid receptors can bind directly to and regulate DNA (ie. activation)
what is the purpose of the 5’ methyl cap and 3’ polyAtail?
cap protects against RNAse, polyAtail protects and signals export
how is the polyAtail added?
polyApolymerase will recognize AAUAAA after RNAse cleaves after it and will add random amounts of A
how is splicing performed?
snRNPs will recognize AGGU and AGG(U) of an exon-intron barrier and will bind U1 and U5 while U2 will bind a random A, complex of U12456 will forma lariat structure and excise the intron and splice the exons in one go
ribosomes are creation occurs where mostly?
45S precursor will be formed in the nucleolus which then splits off into 20S for the 40S subunit and the 5S/32S for the 60S subunit which will bind again in cyto
What contributes to cloverleaf pattern of tRNA and what associates with amino acids
base pairing gives structure, post tran modded 3’ CCA carries AA
Why is actinomycin D too dangerous for clinical use?
sterically hinders replication and transcription
what drugs can treat tuberculosis and meningitis and how?
rifampin inhibits initiation by binding to beta unit of RNA poly and inhibiting initial formation of phosphodiester bond
what bacterial transcription mechanism prevents elongation?
streptolydigin
how does alpha amatin work
toxin from deathcap inhibits euk RNA pol II and thus blocks mRNA synth -> can lead to death or liver failure
