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Lecture 8 RNA modifications - Coggle Diagram
Lecture 8
RNA modifications
Exclusive to eukaryotes
5 prime cap
Poly A tail
Differential RNA processing
Splicing
Normal splicing
Produces canonical protein
All introns removed, exons join
Alternative splicing
Types
Cassette exon
Middle exon included/excluded
Mutually exclusive exons
2 or more adjacent exons, only 1 in mature mRNA
Alternative 3' splice site
3' site of exon included/excluded
Alternative 5' splice site
5' site of exon included/excluded
Produces different isoforms of
canonical protein
Have different effects (eg. 1 isoform inhibit apoptosis, other isoform of same protein induces apoptosis)
DSCAM
38,016 isoforms
Each neuron = different isoform DSCAM
Expressed in
dendrites
Same isoform (same neuron, different dendrites) = self-repulsion
DSCAM mutation
Dendrites stick together
Overexpression
Down syndrome
Maternal factors
Knock-out maternal factors
Cell divison & no nuclear division
Transcript stabilization in Xenopus
Maskin connects CBEP at 3' UTR to 5' cap
Progesterone from ovulation activates kinase
Kinase phosphorylates CPEB
Displacement of maskin allows addition of poly A tail
Myostatin
Negative growth regulator of muscle growth
Myostatin deficiency
Intron inclusion = abrupt stop codon
Non functional protein = increased muscle growth
Spatial control of mRNA
microRNA
Single strand short RNA
binds complementary 3' UTR of mRNA
Silences expression
Blocks ribosome physically
RNA-induced silencing complex (RISC)
Argonaute
Endonuclease in RISC
cleaves mRNA
miR430
Binds maternal factors in zebrafish
Turns them off
Transition to zygotic genome