Flashcards in 3. Transcription and RNA Processing Deck (39):
Most abundant type. Structural component of ribosome
Second most abundant type. Carry amino acids to ribosome.
Specifies amino acid sequence
Heterogenous nuclear RNA (hnRNA, pre-mRNA)
Only in nucleus, precursor of mRNA
Small nuclear RNA (snRNA)
Participates in splicing (removal of introns) of mRNA
Prokaryotic RNA polymerase (2)
- Synthesizes all types of RNA
- Core: alfa2,betabeta'.
Required for initiation of transcription in prokaryotes (helps RNA polymerase to recognize promotor region), released immediately after initiation
Sometimes needed to terminate transcription in prokaryotes
Inhibits prokaryotic RNA polymerase
Binds to DNA, prevents transcription (pro- and eukaryotes)
Three eukaryotic RNA polymerases + function
- RNAP I: nucleolus, 28S, 18S and 5.8S rRNAs
- RNAP II: nucleoplasm, hnRNA/mRNA, some snRNA
- RNAP III: nucleoplasm, tRNA, soms snRNA, 5S rRNA
Transcription factor IID
RNA polymerase II
- Toxin from certain mushrooms
- Inhibits RNA polymerase II
Binding site for RNA polymerases
First base transcribed as RNA
DNA coding strand is identical to..
DNA template strand is..
Used for transcription
Bacterial/prokaryotic promotor contains two consensus sequences..
1. Pribnow box (TATA box)
2. -35 sequence
GC-rich hairpin (=stem + loop) + 6-8 U residues (in newly formed RNA)
Rho binds to newly formed RNA and displaces RNA polymerase from 3' end of RNA. Also stem and loop (G-C rich hairpin)
In bacteria translation and transcription..
Can occur simultaneously (no processing of mRNA, no introns)
Prokaryotic ribosomes bind to..
Shine Dalgarno sequences in 5' UTR
Protein in synthesized from.. to..
Amino terminus (5') to carboxyl terminus (3')
Related genes groups together are transcribed as one unit (eg lactose operon)
Only in bacteria
Eukaryotic promotor contains two consensus sequences..
1. TATA box (-25, Hogness)
2. CAAT box (-70)
Posttranscriptional processing of mRNA in eukaryotes (2)
1. 7-methylguanosine cap to 5' end
2. Poly-A-tail to 3' end
While still being synthesized: ribosome binding site + protection from degradation
- Poly-A addition signal is AAUAAA, cut by endonuclease
- Poly-A-polymerase adds poly-A tail (200 As)
- Protects from degradation and aids in transport
Removes introns, lariat structure is degraded
Complexes of snRNA and protein (snRNP, snurp)
Example alternative splicing (2)
- Tropomyosin and troponin T
- Immunoglobulins (membrane-bound or secreted)
How can alternative splicing be detected?
By Northern Blot
- 40S and 60S -> 80S ribosome
- RNAPI (45S -> 28S, 18S, 5.8S)
- RNAPIII (5S)
- 50S and 30S -> 70S ribosome
- 50S = 5S and 23S
- 30S = 16S
Shiga toxin and Verotoxin (ETEC)
Inactivate 28S rRNA in 60S subunit. RNA glycosylases remove single adenine residue from 28S, prevents aminoacyl-tRNA binding to ribosome.