RNA Part 2 Flashcards
Key differences in transcription between eukaryotes and prokaryotes
Genes and their spacing?
Eukaryotes typically have more genes that are spaced further apart
Key differences in transcription between eukaryotes and prokaryotes
RNA pol?
Eukaryotes have 4 RNA polymerases
Prokaryotes have 1
Key differences in transcription between eukaryotes and prokaryotes
What do eukaryotes have the prokaryotes dont?
Nucleus
How is DNA in eukaryotes packaged?
Into chromatin
In eukaryotes, _ are exported from the nucleus prior to translation
Transcripts
What are the 3 RNA polymerases
RNA pol I
RNA pol II
RNA pol III
RNA pol I responsibility
Recruits the ribosome and rRNA
rRNA genes except 5s
RNA pol II responsibility?
Transcribes protein-coding genes and a variety of noncoding RNAs
RNA pol III responsibility
tRNAs, some snRNAs, 5s rRNA
Most eukaryotes have multiple if not many, _ copies of rDNA genes
tandem
RNA pol II recruitment and activation
What is a preinitiation complex (PIC) ?
A number of general transcription factors cooperate to form the PIC
What does the PIC do?
PIC recruits additional transcription factors and RNA pol II
How do you enable elongation?
A kinase phosphorylates RNA pol II and other proteins to enable elongation
What does the architecture of RNA pol III recruitment and activation depend on?
What does that mean?
Depends on the promoter type.
Different promoters regulate different genes
What is RNA pol II regulated by?
RNA pol II is regulated at multiple steps by carboxyl-terminal domain (CTD) posttranslational modification
How many models did we go over for how RNA pol II terminates
2
First model of RNA pol II termination?
An exonuclease causes RNA pol II to dissociate
Second model of how RNA pol II terminates?
The cleavage of mRNA causes a conformational change in RNA pol II
What are RNA pol II transcripts capped with at the 5’ end?
Capped with 7-methylguanosine to provide protection
What does 5’ end capping involve?
Capping involves the sequential action of 3 enzymes associated with the CTD
How are the 3’ end of RNA pol II transcripts protected?
Protected by polyadenylation, poly-A binding proteins come in and protect the 3’ end
Addition of the poly-A tail involves _ of the mRNA followed by polyadenylation
Cleavage
mRNA splicing
What acts at the 5’ splice junction?
u1 small nuclear ribonucleoprotein
snRNP
mRNA splicing
Normal splicing involves specific pairing between
U1 snRNA and the splice site
mRNA splicing
What could disrupt splicing
Mutations at the splice site
What can suppress some splice site mutations?
Secondary mutation in the U1 snRNA
What do U1 and U2 snRNPs enable?
They enable the formation of the spliceosome and intron excision
How does splicing proceed?
Through a series of transesterification reactions
What organisms have self-splicing introns?
Some bacteria, viruses and nuclear-encoded organellar genes
What are self-splicing introns?
Ribozymes
What does alternative splicing produce?
Related but distinct protein isoforms
In eukaryotes, how can a single gene produce a variety of transcripts?
Splicing makes this possible
A single pre-mRNA that contains exons and introns can be _ in a myriad of patterns
spliced
What enables the formation of spliceosome and intron excision?
U1 and U2 snRNP
Splicing proceeds through a series of _ reactions
Transesterification
What organisms have self splicing introns
Some bacteria, viruses and nuclear encoded organellar genes
Self-splicing introns are _
ribozymes
How can you produce distinct protein isoforms?
Alternative splicing
In eukaryotes, how is it possible for a single gene to produce a variety of transcripts
Splicing makes this possible
a single pre-mRNA that contains exons and introns can be spliced in a myriad of _
Patterns
There are _ mechanisms for mRNA decay in eukaryotes
multiple
_ or _ RNA can result in gene silencing
Exogenous or ectopic
How are small interfering RNAs (siRNAs) produced ?
By hairpin or double stranded RNAs
_ processes siRNAs to enable them to complex with _
Dicer
Argonaute (Ago)
The Ago complex is further processed and is able to target the _ _
Complementary mRNA