Cellular RNA Flashcards
what are the 3 events that take place in EUK termination
RNA pol II falls off
RNA trimmed
RNA polyadenylation is added
what are the two models for Eukaryote transcription termination
Torpedo model
Allosteric model
torpedo model
exonuclease XRN2 chews back RNA and kicks off RNA pol II when the two proteins collide
Allosteric model
PolyA tail on mRNA signals RNA pol II to change shape and fall off
what are the two models for Prokaryotic transcription termination
Rho protein facilitates
RNA secondary structure facilitates (hairpin)
What is the order for modifying proteins
Capping proteins
slicing proteins
polyadenylation proteins
Why do RNAs make 3D shapes
RNA are single stranded so their nitrogenous bases want to pair with their complementary bases
what the RNA complex structures good for
becoming binding sites for proteins
What is a 5’ cap
an upside down and backwards Guanine with an extra methyl group at the 5’ end of an RNA
what does a 5’ cap do
Resistant to digestion by nucleases
Right shape to be recognized by the CBC proteins
Processing mRNA and start translation
What do CBC proteins do
Initiate splicing and polyadenylation
Direct mature mRNA through the nuclear pores
Recruit translation initiation factors (eIFs)
Group I introns
most basic form
all life has them
self removed
yields either linear or circularized introns
Group II introns
Prok and Euks organelles have them
makes lariat structures
{probably} can remove themselves
Precursors to spliceosomal introns
Spiceosomal introns
most advance structure of a group II intron
Euks only
Removed by proteins
creates a lariat structure
tRNA introns
Euks and organelles have them
removed by proteins
tRNA split and re-ligated
Alternative splicing
increase genetic diversity without permanent changes to the DNA sequence
PABPs (polyA binding proteins)
bind to elFs to circularize the mRNA and start translation
When does polyA tail happen
as we are finishing up transcription
what does CPSF do
bind to the poly signal site
What does CstF do
cleaves stimulation factor to downstream element DSE site
What does PAP do?
adds on the tail
what do PABPS
coat the tail in order to protect it from being chewed away
Genes transcribed by RNA pol I
rRNA genes
Genes transcribed by RNA pol II
all protein-coding genes plus snoRNA genes, miRNA, siRNA, LncRNA, most snRNA
Genes transcribed by RNA pol III
tRNA genes
What are small Nuclear RNAs (snRNAs)
mid range in size and part of the spliceosome
What are small Nucleolar RNAs (snoRNAs)
mid range in size and primary function is chemical modification of nucleic acids
Where are rRNAs made
in the nucleolus
What are microRNAs (miRNAs)
small in size
block translation by degrading RNAs
they are hairpin in shape with a buldge
What are small interfering RNAs (siRNAs)
Small in size
Main function is to block translation by degrading RNAs
They do no have a bulge or a hairpin just a segment of dsRNA
What is transcriptional silencing by siRNAs
requires sequences homology
spreads a methyl mark
what is PIWI-interacting RNAs (piRNAs)
Small in size
Main function is to silence transposons by methylating their DNA
What is Long noncoding RNAs (IncRNAs)
large in size
not common function
