Sandbox 502
From Proteopedia
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==Role in Pre-mRNA splicing== | ==Role in Pre-mRNA splicing== | ||
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| + | The Lsm complex 2-8 is involved in pre-mRNA splicing through association with the 3’terminal poly(U) tract of U6 snRNA. While the exact mechanism by which it acts is unclear it is thought that the Lsm 2-8 complex provides stability and function to the U6 snRNP. For example, several experiments using mutants with point mutations of the Lsm proteins 2-8 have shown defects in splicing that correlate with low levels of U6 snRNA. It may also play a role in the various rearrangements that are necessary throughout the splicing cycle. In fact, it has been shown to be important in the assembly of U4-U6 di snRNP and U4-U5/U6 tri snRNP (He). | ||
==Role in mRNA decay== | ==Role in mRNA decay== | ||
Revision as of 20:20, 4 July 2012
Lsm
by Kelly Hrywkiw Template:STRUCTURE 4emg
Contents |
Introduction
Sm-like (Lsm) proteins most closely resemble Sm proteins, both of which are found in all three domains of life (Wu). Sm proteins play a large role in spliceosome biogenesis through mediating U1, U2, U4, U5, and U6 snRNP assembly. The Sm proteins can be broken down into seven specific proteins (SmB, SmD1, SmD2, SmD3, SmE, SmF, and SmG in humans) all of which share a conserved Sm motif. The Lsm proteins also share the Sm motif, with a total of nine specific Lsm proteins found in yeast (Lsm1-Lsm9). The Lsm proteins 2-7 most closely resemble Sm proteins D1-G, where Lsm 1 and 8 most closely resemble the SmB proteins (He). Lsm9 does not appear to resemble any of the Sm proteins, although there have been some related structures found in the archaeal genome (He). Several studies have shown that the Sm proteins form into seven membered rings which bind to the sm binding site, a U rich sequence found in all but U6 snRNA. Similarly, Lsm proteins have been found to associate into three complexes, Lsm2-8, Lsm1-7, and Lsm2-7 (Wu). The exact mechanisms of these complexes are dictated by their composition, structure, and cellular location and their overall functioning in pre-mRNA splicing, mRNA decay, and other additional roles (Wu) (He).
Role in Pre-mRNA splicing
The Lsm complex 2-8 is involved in pre-mRNA splicing through association with the 3’terminal poly(U) tract of U6 snRNA. While the exact mechanism by which it acts is unclear it is thought that the Lsm 2-8 complex provides stability and function to the U6 snRNP. For example, several experiments using mutants with point mutations of the Lsm proteins 2-8 have shown defects in splicing that correlate with low levels of U6 snRNA. It may also play a role in the various rearrangements that are necessary throughout the splicing cycle. In fact, it has been shown to be important in the assembly of U4-U6 di snRNP and U4-U5/U6 tri snRNP (He).
