BIO206H5 Lecture Notes - Lecture 10: Exon Junction Complex, Rna Splicing, Nuclear Pore

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1 Dec 2013
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Enhancers & Repressors
Upstream transcription factors activating or repressor
- Associated with 4 areas of chromosomes (they need to be all in place before polymerase can begin
transcription)
introns removed & exons spliced together
requires small nuclear ribonucleoprotein particles (snRNPs - “snurps”) = proteins + snRNAs
Collectively: complex of snurps = spliceosome
occurs in nucleus after capping and before tailing
Cotranscriptional processing
Introns need to be physically removed, exons need to be spliced together (done by
spliceosome)
RNA splicing: Intron Removal
Conserved splice sites
Exon/Intron junction
RNA Splicing - Reaction Mechanism
Lecture 10
October-15-13
2:12 PM
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Spliceosome
Forms during transcription
Identifies & Excises Introns- Splices Exons
small nuclear RiboNuclearProteins (snurp)
An assembly of 5 snRNPs complexes
Macromolecular Protein & RNA super-complex
small nuclear RNA (snRNA) - 5 snRNA + more than 60 polypeptides
snRNP U1 = proteins + snRNA U1
RNA splicing: The players
Previously reported consensus branch point sequences
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Note how U2 binds to the 2 bases on either side of the branch point adenosine & leaves that
one sticking out.
U1 has complimentary sequence to 5’ splice site
SnRNP bind complimentary to the RNA sequence
SR proteins are Serine arginine rich proteins that bind to RNA
Splicing process:
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Document Summary

Associated with 4 areas of chromosomes (they need to be all in place before polymerase can begin transcription) Rna splicing: intron removal introns removed & exons spliced together requires small nuclear ribonucleoprotein particles (snrnps - snurps ) = proteins + snrnas. Collectively: complex of snurps = spliceosome occurs in nucleus after capping and before tailing incompletely processed mrnas are not exported from nucleus. Introns need to be physically removed, exons need to be spliced together (done by spliceosome) An assembly of 5 snrnps complexes small nuclear ribonuclearproteins (snurp) snrnp u1 = proteins + snrna u1 small nuclear rna (snrna) - 5 snrna + more than 60 polypeptides. Note how u2 binds to the 2 bases on either side of the branch point adenosine & leaves that one sticking out. U1 has complimentary sequence to 5" splice site. Sr proteins are serine arginine rich proteins that bind to rna.

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