5. Transcription Flashcards
which RNA is most highly regulated
mRNA
differences between DNA pol and RNA pol?
DNA pol requires primer
RNA pol does not require primer
New DNA remains hybridized to DNA templated–forming semiconservatie double stranded
New RNA does not remain hybridized (single strand)
DNA is relatively permanent
RNA has short half life
RNA production is less accurate (because not as serious if mistakes made)
different structures
which RNA codes for proteins
mRNA
which RNA synthesizes proteins
rRNA, tRNA
which RNA aids in splicing
snRNA
which RNA processes proteins
snRNA, snoRNA
direction RNA pol travels down template strand?
3’ to 5’
direction RNA pol travels down non-template/sense/coding strand?
5’ to 3’
how do you recognize the template strand?
it’s the strand upon which transcription occurs
the further downstream RNA pol travels?
the longer the RNA becomes
the longer transcripts are in the direction RNA pol is traveling
which eukaryotic RNA pol mostly transcribes rRNAs?
I
which RNA is most heavily transcribed and represented in the cytoplasm
rRNA
which eukaryotic RNA pol is most highly regulated?
II
which eukaryotic RNA pol transcribes rRNA subunits, most tRNAs, and snRNAs?
III
which eukaryotic RNA pol transcribes mRNA?
II
which RNA pol requires only a single protein for initiation, and what is that protein?
bacterial, sigma factor
the promoter
consists of dsDNA
5’ flanks (upstreams) the coding region
contains conserved sequences that proteins bind
functions of promoter
dictates directionality
featured in core promoter (TATA, B response element, CCAAT box)
regulation
transcription unit contains?
DNA binding domain (probs)
transactivation domain (definitely)
TFIID
binds to directionality core promoter sequences, largest of the TFs
TBP
part of TFIID, recognizes TATA box
interactions between TFs
TFs overlap 5’ flanking region, initiation site, and some sites downstream of initiation site
create an environment RNA polymerase can bind to
RNA polymerase domains: CTD
C-terminus domain
binding site for accessory proteins to generate mRNA
when CTD is phosphorylated?
releases transcription factors so RNA polymerase can take off downstream on DNA< transcribing the template stand as it goes
RNA pol II
functions as “RNA factory”
carries functionsal proteins that contibute to generation of mRNA
has capping factors, splicing factors, end processing proteins (CPSF & CstF)
elongation: superhelical tension/supercoiling
as we unwind DNA, we induce helical turns, resulting in negative supercoiling upstream & pos supercoiling downstream
ultimately facilitates strand separation
eukaryotic mRNA contains?
introns & exons
5’cap & poly-A tail
5’ cap
aids mRNA nuclear export
protects from 5’ to 3’ exonuclease degradation in cytoplasm
targets transcripts to ribosome for translation
poly-A tail
participates in termination of transcription
aids mRNA nuclear export
protects from 3’ to 5’ exonuclease degradation in cytoplasm
targets transcripts to ribosome for translation
splicing
removing introns, joining exons
splicesosome
complex of snRNA’s and proteins that bind to intron/exon sites & create Lariat structures (loops) and intron removal
alternative splicing
every gene can have multiple transcripts
exon definition
exon sizes fairly uniform, relatively short compared to introns
termination
consensus nucleotide sequences that direct clevage and polyadenylation to form the 3’ end of a eukaryotic mRNA
transcription won’t begin until?
poly a tail binds to 5’ cap
purpose of poly A tail?
lengthens half life of mRNA, makes it more likely to be translated
purpose of 5’ cap?
keeps mRNA “alive”
