Yeast Sm-like proteins function in mRNA decapping and decay

Tharun, Sundaresan; He, Weihai; Mayes, Andrew E.; Lennertz, Pascal; Beggs, Jean D.; Parker, Roy

doi:10.1038/35006676

Cited by 394 publications

(485 citation statements)

References 22 publications

(31 reference statements)

Supporting

Mentioning

454

Contrasting

Unclassified

Order By: Relevance

“…To assess the RNA dependence of proteinprotein interactions, lysates were treated with RNAseA at 0.5 μg μl −1 for 20 min at room temperature before immunoprecipitation procedures as described in ref. 18.…”

Section: Cell Culture and Transfectionmentioning

confidence: 99%

MicroRNA-dependent localization of targeted mRNAs to mammalian P-bodies

et al. 2005

Self Cite

View full text Add to dashboard Cite

Small RNAs, including small interfering RNAs (siRNAs) and microRNAs (miRNAs) can silence target genes through several different effector mechanisms1. Whereas siRNA-directed mRNA cleavage is increasingly understood, the mechanisms by which miRNAs repress protein synthesis are obscure. Recent studies have revealed the existence of specific cytoplasmic foci, referred to herein as processing bodies (P-bodies), which contain untranslated mRNAs and can serve as sites of mRNA degradation2-7. Here we demonstrate that Argonaute proteins -the signature components of the RNA interference (RNAi) effector complex, RISC -localize to mammalian P-bodies. Moreover, reporter mRNAs that are targeted for translational repression by endogenous or exogenous miRNAs become concentrated in P-bodies in a miRNA-dependent manner. These results provide a link between miRNA function and mammalian P-bodies and suggest that translation repression by RISC delivers mRNAs to P-bodies, either as a cause or as a consequence of inhibiting protein synthesis.RNAi was initially characterized as a post-transcriptional gene silencing mechanism in which the experimental introduction of long double-stranded RNAs (dsRNAs) induces sequencespecific destruction of homologous mRNAs (reviewed in ref. 1). RNAi pathways are initiated when dsRNAs are processed by Dicer into siRNAs of 21-26 nucleotides. siRNAs are incorporated into the effector complex RISC. In RISC, the siRNA is bound by an Argonaute protein, which uses the sequence of the siRNA to select and cleave complementary substrates (reviewed in ref. 8).RISC can also silence gene expression by preventing protein synthesis. Genetic studies of Caenorhabditis elegans that are mutant for Dicer forged the initial link between a previously known class of small regulatory RNAs, the stRNAs, and the RNAi pathway9-13. Subsequent studies showed that stRNAs are archetypes of a large class of regulatory RNAs, known as miRNAs (reviewed in ref. 14). Although miRNA and siRNA pathways can be biochemically compartmentalized, both types of RNAs enter RISC, bind to Argonaute proteins and identify their silencing targets in conceptually similar ways. They differ, at least in animals, in that miRNAs most often pair imperfectly with their targets and are thus unable to direct Argonautemediated cleavage15. Instead, miRNAs repress protein synthesis in a cleavage-independent fashion8,14,15.3 Correspondence should be addressed to G.J.H. (e-mail: hannon@cshl.org) and R.P. (e-mail: rrparker@u.arizona.edu).Note added in proof: After this study had been accepted for publication, Sen and Blau30 reported similar observations of the localization of human Ago2 to cytoplasmic P-bodies.Note: Supplementary Information is available on the Nature Cell Biology website. The mechanism by which miRNAs repress translation of their target mRNAs is unknown. Conceivably, RISC could prevent protein synthesis from miRNA targets in one of several ways. RISC could affect translation, per se, by altering rates of initiation or elongation by the riboso...

show abstract

Section: Cell Culture and Transfectionmentioning

confidence: 99%

MicroRNA-dependent localization of targeted mRNAs to mammalian P-bodies

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…These results were almost identical to those obtained in K. lactis and confirmed that the lack of the C-terminal region of the protein severely affects cell viability during the stationary phase. In S. cerevisiae, the role of Lsm4p has been associated with mRNA splicing and decapping (Bouveret et al, 2000;Mayes et al, 1999;Thaurun et al, 2000) and work is in progress to verify whether these processes are altered in the K. lactis and S. cerevisiae strains expressing the truncated form of KlLsm4p. Cells were grown on YPD medium and OD 600 was measured at the indicated times.…”

Section: Complementation Of S Cerevisiaementioning

confidence: 99%

Isolation and study of KlLSM4 , a Kluyveromyces lactis gene homologous to the essential gene LSM4 of Saccharomyces cerevisiae

Mazzoni

Falcone

2001

Yeast

View full text Add to dashboard Cite

We have isolated the KlLSM4 gene as a multicopy suppressor of a Kluyveromyces lactis mutant which shows a rag x phenotype (resistance to antimycin A on glucose). This gene is homologous to the ScLSM4 of Saccharomyces cerevisiae, which codes for an essential 187 amino acid protein containing Sm-like domains. These motifs are present in the evolutionarily conserved family of the Sm-like proteins, which are involved in a large number of cellular processes, including pre-mRNA splicing and mRNA decapping. We demonstrated that the first 72 amino acids of KlLsm4p, which contain the Sm-like domains, can restore cell viability in both K. lactis and S. cerevisiae cells lacking the wild-type protein. However, the absence of the carboxy-terminal region resulted in a remarkable loss of cell viability in the stationary phase. The KlLSM4 sequence has been deposited in the EMBL Data library under Accession No. AJ311719.

show abstract

“…The process and regulation of mRNA turnover is a fundamental aspect of gene expression+ A major pathway of mRNA turnover for both stable and unstable transcripts has been identified in Saccharomyces cerevisiae+ In this pathway, degradation is initiated by deadenylation of the 39 poly(A) tail (Muhlrad & Parker, 1992;Decker & Parker, 1993)+ In yeast, deadenylation is followed by removal of the 59 m7 GpppN cap structure, and exonucleolytic digestion in a 59-39 direction (Decker & Parker, 1993;Hsu & Stevens, 1993;Beelman et al+, 1996)+ Poly(A) shortening requires two proteins, Ccr4p and Pop2p, which have recently been shown to be components of the yeast deadenylase )+ Following deadenylation, the Dcp1p/Dcp2p decapping complex decaps mRNAs at their 59 end Dunckley & Parker 1999)+ Although Dcp1p and Dcp2p are the only proteins known to be required for decapping (Dunckley & Parker, 1999, the rate of decapping is affected by several trans-acting factors+ These accessory factors include Pat1p/Mrt1p, the Lsm complex (consisting of Lsm1p-Lsm7p), Vps16p, Edc1p, and Edc2p Zhang et al+, 1999;Bonnerot et al+, 2000;Tharun et al+, 2000;Wyers et al+, 2000;Dunckley et al+, 2001)+ Pat1p/Mrt1p was originally identified as a genetic lesion that slows mRNA decapping, and was later shown to also be required for efficient translational initiation Wyers et al+, 2000)+ There are nine Lsm proteins in yeast, which form two distinct seven-member ring structures of differing function (Salgado-Garrido et al+, 1999)+ Lsm2p-Lsm8p associate in the nucleus and are involved in U6 snRNA metabolism, whereas Lsm1p-Lsm7p associate in the cytoplasm and affect decapping of mRNAs (Mayes et al+, 1999;Bouveret et al+, 2000;Tharun et al+, 2000)+ Vps16p was identified as a mutant that affected decapping rates in vitro, and Edc1p and Edc2p have been shown to be in a complex with Dcp1p and Dcp2p (Zhang et al+, 1999;Dunckley et al+, 2001)+ Although the mechanism of how these proteins en-hance decapping is unclear, it is possible a class of decapping enhancers may do so by directly affecting the translatability of the mRNA+ Indeed, translational repression may be a first step required for efficient decapping, as recent studies have shown the cap-binding protein, eIF-4E, can inhibit decapping activity both in vivo and in vitro (Schwartz & Parker, 1999+ Given this, a critical issue to resolve in understanding mRNA decay is to determine the nature of transitions between translating and nontranslating states of mRNAs+…”

Section: Introductionmentioning

confidence: 99%