function of the ski4p (csl4p) and ski7p proteins in 3’-to- 5’ degradation of mrna ambro van...
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Function of the Ski4p (Csl4p) and Ski7p Proteins in 3’-to-5’ Degradation of mRNA
Ambro van Hoof, Robin R. Staples, Richard E. Baker, and Roy Parker
Molcecular and Cellular Biology, p8230-8243 (2000)
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Yeast virus
Introduction
Annu. Rev. Genet. 30:109-39 (1996)
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Cryo-EM 16Å Crystal structure 3.4Å
Annu. Rev. Microbiol. 46:347-75 (1992)
J. Mol. Recognit. 18:158-168 (2005)
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The viral replication cycles of L-A and its satellites
Annu. Rev. Genet. 30:109-39 (1996)
J. Cell. Biol. 138:975-985 (1997 )
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SKI antiviral system
Trends. Microbiol. 1:294-298 (1993)J Bacteriol. 136(3): 1002–1007 (1978)
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A60-80mRNA7mGppp
mRNA degradation in yeast
A0-10mRNA7mGpppA60-80mRNA p
DeadenylationDecapping (Dcp1p, Dcp2p)
A60-80mRNA
5’-3’ degradation (Xrn1p)
mRNA7mGppp
3’-5’ degradation
The exosome: a conserved eukaryotic RNA processing complex containing multiple 3’-5’ exoribonuclease activities. Cell, 91, 457-466 (1997)
Rrp4p,Rrp41/Ski6p, Rrp42p, Rrp43p, Rrp44p
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The 3’ to 5’ degradation of yeast mRNAs is a general mechanism for mRNA turnover that requires the SKI2 DEVH box protein and 3’ to 5’ exonucleases of the exosome complex EMBO J. 1497-1506 (1998)
The SKI2, SKI3, SKI6/RRP41, SKI8 and RRP4 gene products are required for 3’ to 5’ decay of mRNA
The yeast antiviral proteins Ski2p, Ski3p, and Ski8p exist as a complex in vivoRNA 6:449-457 (2000)
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The ski4-1 and ski7Δ mutations affect the metabolism of a degradation intermediate of MFA2pG mRNA
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The ski4-1 and ski7Δ mutations stabilize a degradation intermediate of MFA2pG mRNA
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Strains containing either ski4-1 or ski7Δ in combination with dcp1-2 or dcp2-7 are not able to grow under conditions restrictive for the decapping defect
SKi4p and Ski7p proteins are required for 3’-5’ mRNA degradation as are the components of the exosome and the Ski2p,SKi3p, and Ski8p protein.
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The ski4-1 mutation is complemented by a wild-type (WT) CSl4 gene
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A mutation in the conserved S1 RNA binding domain of Csl4p is responsible for the ski4-1 phenotype
Two mutations of Ski4p : R65K, G253E
The SKI4 gene is identical to the CSl4 gene
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The ski4-1 mutation does not affect all Csl4p functions
ski6
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The csl4-1 mutation affects rRNA processing but not mRNA degradation
rRNA processing
mRNA degradation
The ski4-1 allele genetically separates the functions of the exosome in rRNA processing and mRNA decay
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The ski7Δ and hgs1Δ mutations do not affect 5.8S rRNA or U4 snRNA processing or 5’ ETS degradation
The SKI7 gene is specifically required for mRNA degradation by the exosome
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Summary
1. The Ski4p and Ski7p proteins are required for mRNA degradation.
2. The SKI4 gene is identical to the CSL4 gene
3. The ski4-1 allele genetically separates the functions of the exosome in rRNA processing and mRNA decay
4.The SKI7 gene is specifically required for mRNA degradation by the exosome.
SKI 1: Xrn1p enzyme (5’ to 3’ exoribonuclease)SKI 2: 1287 a.a. putative RNA helicaseSKI 3: 1432 a.a. tetratricopeptide repeat (TRP) proteinSKI 4: 195 a.a. S1 domain (Csl4p)SKI 6: 264 a.a. Rrp41p (3’-5’ exoribonuclease) SKI 7: 747 a.a. GTPase domain ( translation elongation factor EF1A/ translation termination factor eRF3)SKI 8: 397 a.a. five WD-40 (beta-transducin) repeats protein
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Componenets of the exosome complex