29 - RNA Processing; Capping and Polyadenylation

29 RNA - Spliceosome 1 Current model of spliceosomal splicing First two steps Lodish 3rd edition 1 U1 attaches to 5 splice site of intron(due to

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Spliceosome
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 •First two steps: Current model of spliceosomal splicing 1. U1 attaches to 5 splice site of intron (due to the complementarity between sequences) 2. U2 binds to branch point A (again, due to complementary sequences). This step requires ATP (A complex). “A” residue is unpaired – available to react •Lodish, 3 rd edition
Background image of page 2
3 Current model of spliceosomal splicing, cont. 3. U4/U6 (extensively base paired with each other) and U5 bind; tri- complex binds to 3’ intron splice site (again, due to complementarity between U5 and 3’ intron splice site); U4 is inhibitor of U6 4. U4 and U6 change conformation due to the binding. Assembly of the spliceosome (B1 complex) is complete. 1. U1 attaches to 5 splice site of intron (due to the complementarity between sequences) 2. U2 binds to branch point A (again, due to complementary sequences). This step requires ATP (A complex). •Weaver, 2 nd edition
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 5. U6 dissociates from U4, displacing U1 at the 5’ splice site (with blue exon); U1 and U4 are released. ATP-dependent step. 6. Once U1 and U4 are released, the splicesome is activated; it contains only U2, U5 and U6 snRNPs (B2 complex); U2-U6 represent the active site of the splicesome Current model of spliceosomal splicing, cont. •Weaver, 2 nd edition
Background image of page 4
5 7. U5 is responsible for positioning and holding; U2-U6 complex has catalytic activity (ribozyme): mediates splicing at both sites- very fast (formation of C1 and C2 complexes); 7. Second splicing step requires ATP 8. Lariat degraded, making splicing irreversible 9. snRNPs are probably released as individual particles and recycled Current model of spliceosomal splicing, cont. •Weaver, 2 nd edition
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 Nature Reviews Molecular Cell Biology 4, 960-970 (December 2003) Interactions are possible due to the complementarities of the sequences (between Us and RNA and Us themselves) U4 inhibits U6
Background image of page 6
7 What is catalytically active component of snRNP? Pre-mRNA are spliced by same reactions that occur in self-splicing group II introns The snRNAs required for splicing are very similar to parts of the self- splicing group II introns; combined snRNAs ( U6 and U2 ) have similar structure (conformation) to the structure of self-splicing group II introns snRNA are catalytically active components of snRNPs (ribozyme) Proteins probably have supplementary role: sites of interaction with regulatory factors, maintaining of proper 3D structure, transport (similar to the role of maturases)…
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
8 Transcription initiation •Direct influence of A and R on initiation •Chromatin remodeling and histone modifications •Methylation •Hormones and other “external” signals RNA processing •Alternative splicing and trans-splicing •polyadenylation Transport through the nuclear pore Posttranscriptional / pretranslational control (events on/with mRNA before ribosomes) •Localization of mRNA •RNA editing •Post-transcriptional silencing by siRNA or miRNA
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/23/2011 for the course BIOL 308 taught by Professor Miskovic during the Fall '09 term at Waterloo.

Page1 / 24

29 RNA - Spliceosome 1 Current model of spliceosomal splicing First two steps Lodish 3rd edition 1 U1 attaches to 5 splice site of intron(due to

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online