Exam 1 - mRNA Processing Flashcards
what is are the three most important structures in a mRNA
1 - 5’ cap
2 - splicing proteins (internal)
3 - 3’ (poly a tail)
Describe the 5’ cap and what it does
upside down and backwards guanine with methyl group
1 - resistant to digestion nucleus
2 - Has CAP binding proteins that:
a) initiate splicing and adding a poly a tail
b) direct mature RNA though nuclear pore
c) recruit translation IF (eIF’s)
What are the 4 splicing introns
1 - Group 1 introns
2 - Group 2 introns
3 - spiceosomal introns
4 - tRNA/archaeal introns
Group 1 introns
-found in prokaryotes, eukaryotes, and organelles
REMOVED BY:
- found in rRNA genes in eukaryotes
- self catalyzed
- linear or circular intron
Group 2 introns
- found in prokaryotes, eukaryotes, and organelles
REMOVED BY: - self catalyzed
- some require protein helper
- lasso structure
Splicesomes
- EUKARYOTES ONLY
REMOVED BY:
-protein mediated (splicesome) - Lasso structure
Spliceosome is a mixture of
RNA and protein
tRNA/ archaeal intron
-found in eukaryotes and organelles and archaebacteria
REMOVED BY:
- protein mediated
a) endonuclease - removes
b) ligase: reconnects
What is alternative splicing
- a way to increase genetic diversity
- does not change DNA sequence
what is polyadenylation and function
200-250 adenines at the 3’ tail of RNA
-defines exact 3’end of the RNA
- has a PABP that is resistant to digestion of the nucleus and binds to eIF to circularize the mRNA and start translation
CPSF to ___________ and
CstF downstream to _________
1 - polyadenylation signal site
2 - DSE site
what does PAP and PABP do
PAP = adds a tail
PABP = coats the tail
Noncoding RNA makes up ____ of all RNA
98%
what is the only coding RNA
mRNA - messenger RNA codes for proteins
snRNA
Name:
Transcribed:
Size:
Role:
- small nuclear RNA
-RNA pol 1 and 2 - mid range
- part of splicosome
snoRNA
Name:
Transcribed:
Size:
Role:
- small nucleolar RNA
-RNA pol 2 - mid range
- chemical modification of nucleic acid (tRNA,rRNA,snRNA)
miRNA
Name:
Transcribed:
Size:
Role:
-micro RNA
-RNA pol 2
-small
-inhibit translation hairpin with a bulge
siRNA
Name:
Transcribed:
Size:
Role:
-small interfering RNA
- small
- block translation by degrading RNA
- block transcription by promoting heterochromatin
- no bulge and no hairpin
piRNA
Name:
Transcribed:
Size:
Role:
-PIWI interacting RNA
-RNA pol 2
- small
- silence transposons by methylating DNA
lncRNA
Name:
Transcribed:
Size:
Role:
-long noncoding RNA
- RNA pol 2
- SIGNALL
- xist = coats x chromo to inactivate it
- DECOY
- GAS5 = binds to receptor to prevent signal cascade
-GUIDE
- HOTAIR = localizes HMT
-SCAFFOLD
- physically connects proteins to activated transcription
-ceRNA NETWORKS
- miRNAregualtion
rRNA
Name:
Transcribed:
Size:
Role:
-ribosomal RNA
- RNA pol 1 and 2
- mid range to long
- component of ribosome
- large and small subunits
- 3 binding sites for tRNA
- A.P.E
tRNA
Name:
Transcribed:
Size:
Role:
-transfer RNA
-RNA pol 3
- mid range
- deliver amino acids to growing peptide chain
