KEM1

b>KEM1 is a Saccharomyces cerevisiae gene, conserved in all eukaryotes, whose deletion leads to pleiotropic phenotypes...

..Our results show the first example of an RNA-dependent gene trans-silencing mediated by epigenetic marks in S. cerevisiae...

..Hence, by recruiting Rpb4/7, Pol II governs not only transcription but also mRNA decay...

..These results indicate the involvement of a new conserved Sm-like protein complex and a new factor, Pat1p, in mRNA degradation and suggest a physical connection between decapping and exonuclease trimming...

..These results define the flux of mRNAs between polysomes and P bodies as a critical aspect of cytoplasmic mRNA metabolism and a possible site for regulation of mRNA degradation...

..These observations argue that efficient mRNA turnover is required for viability and that we have identified the two major pathways of mRNA decay in yeast...

..and is shown to be in a complex with the mRNA degradation factor Pat1/Mtr1 and with the 5'-3' exoribonuclease Xrn1. Dhh1 specifically affects mRNA turnover in the deadenylation-dependent decay pathway, but does not act on the ..

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..We propose that 18S NRD and NGD are different observable outcomes of the same initiating event: a ribosome stalled inappropriately at a sense codon during translation elongation...

..We also provide evidence that the process of NGD is conserved in insect cells. On the basis of these results and the process of translation termination, we suggest a multistep model for the process of NGD...

..Our data support a model wherein certain promoters are embedded in a repressive chromatin controlled by cryptic transcription...

..In BY4741, rrp44-exo was synthetic-lethal with loss of the cytoplasmic 5'-exonuclease Xrn1, indicating block of mRNA turnover, but not with loss of the nuclear 3'-exonuclease Rrp6...

..Here we present evidence that the SKI1/XRN1 5'-exonuclease plays a major role in the elimination of the non-viral upstream sequences from the primary ..

..We show here that components of this RTD pathway include the 5'-3' exonucleases Rat1 and Xrn1, and Met22, which likely acts indirectly through Rat1 and Xrn1...

..Thus, we propose that the non-conserved C-terminus of Dhh1p plays a role in defining specific interactions with mRNA regulatory factors that promote distinct mRNA decay...

..These results support a model for transcription termination in which cotranscriptional cleavage by Rnt1p provides access for exoribonucleases in the absence of polyadenylation signals...

..We have identified cytoplasmic P-body components encoded by DHH1, KEM1, LSM1, and PAT1 as cofactors that posttranscriptionally enhance Ty1 retrotransposition...

..These data suggest that eIF2A acts as a switch to regulate IRES-mediated translation, and eEF1A may be an important mediator of translational activation during ethanol stress...

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..In Saccharomyces cerevisiae, the bona-fide regulatory ncRNAs are destabilized by the Xrn1 5'-3' RNA exonuclease (also known as Kem1), but the genome-wide characterization of the entire regulatory ncRNA ..

..cerevisiae cells redirect iron assimilation through the non-reductive pathway to minimize oxidative damage by the ferrous ions, which are formed during iron import through the Ftr1/Fet3 complexes...

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..Mammals may use similar regulatory mechanisms because components of the decay apparatus and signaling pathways are conserved...

..However, mutations in DCP1 and DCP2, encoding a decapping enzyme complex, and XRN1, encoding a 5'-3' exonuclease, restored the decreased MTL1 mRNA levels...

..We also identify numerous direct interactions between Pat1, Dcp1, Dcp2, Dhh1, Scd6, Edc3, Xrn1, and the Lsm1-7 complex...

..Through these associations, Sus1 mediates the nuclear dynamics of different gene loci and facilitate the export of the new transcripts...

..of DDD and NMD explain the strong requirement for general 5' to 3' mRNA degradation factors Dcp1, Dcp2, and Xrn1 in Ty1 retromobility...

..Our data suggest that Rat1p serves to terminate RNAPII molecules engaged in the production of uncapped RNA, regardless of their position on the gene locus...

..Combined with earlier work showing Ded1p can have a positive effect on translation, these results suggest that Ded1p is a bifunctional protein that can affect both translation initiation and P-body formation...

..Overall our findings suggest that NMD is more conserved in evolution than previously thought, and that at least one of the Smg5-7 proteins is conserved in budding yeast...

..Our genetic analyses suggest that Rpb7p plays two distinct roles in mRNA decay, which can both be uncoupled from Rpb7p's role in transcription. Thus, Rpb7p plays pivotal roles in determining mRNA levels...

A mutation in NMD3 was found to be lethal in the absence of XRN1, which encodes the major cytoplasmic exoribonuclease responsible for mRNA turnover...

..Uncapped poly(A)+ SSA4 mRNA accumulated in cells lacking the 5' exoribonuclease Xrn1. These findings provide genetic evidence for the long-held idea that the cap guanylate is critical for mRNA ..

b>XRN1 encodes an abundant cytoplasmic exoribonuclease, Xrn1p, responsible for mRNA turnover in yeast...

..Accordingly, yeast karyogamy has become an important model system to investigate critical functions of the cytoplasmic microtubules and the microtubule organizing center, the nuclear envelope, and the endoplasmic reticulum...

..KEM1 was also independently identified as DST2, SEP1, XRN1 and RAR5 on the basis of DNA strand transferase or exoribonuclease activity in vitro or mutations ..

Strand exchange protein 1 (Sep1) (also referred to as exoribonuclease I [Xrn1]) from Saccharomyces cerevisiae has been implicated in DNA recombination, RNA turnover, karyogamy, and G4 DNA pairing among other disparate cellular processes...

Saccharomyces cerevisiae cells lacking the SEP1 (also known as XRN1, KEM1, DST2, RAR5) gene function exhibit a number of phenotypes in cellular processes related to microtubule function...

Strand exchange protein 1 (Sep1) from Saccharomyces cerevisiae promotes homologous pairing of DNA in vitro and sep1 mutants display pleiotropic phenotypes in both vegetative and meiotic cells...

..The ski1-1 mutation suppresses (bypasses) all mak mutations tested except mak16-1...

We have identified mutations in three genes of Saccharomyces cerevisiae, KEM1, KEM2 and KEM3, that enhance the nuclear fusion defect of kar1-1 yeast during conjugation. The KEM1 and KEM3 genes are located on the left arm of chromosome VII...

..b>ski1/xrn1Delta ski2Delta and ski1/xrn1Delta ski7Delta mutants were viable but temperature sensitive for growth.

The KEM1/XRN1 gene was originally identified because of its functions in microtubule-mediated processes, and is also known to be a major cytoplasmic 5'-3' exoribonuclease gene, which is involved in RNA turnover...

..Furthermore, we find that genes involved in mitotic spindle integrity and positioning have a previously unrecognized role in sister chromatid cohesion...

..show that the temperature-sensitive stu1-5 allele is synthetically lethal in combination with ubp3, gim1-gim5, and kem1 mutations. The primary focus of this article is on the stu1-5 ubp3 interaction...

..A previous genome-wide screen in Saccharomyces cerevisiae, a model host, identified five host genes, including XRN1, encoding a 5'-3' exoribonuclease, whose absence led to an approximately 10- to 50-fold enhancement of RNA ..

..identified by its ability on a high-copy number plasmid to suppress the nuclear fusion defect caused by the kem1 null mutation...

..We propose that nuclear pre-mRNA turnover represents a novel step in the regulation of gene expression...

..is synthetically lethal with the rat1-1(ts) mutation and shows genetic interaction with a deletion of SKI2 but not XRN1. Polysome analysis of an rai1 deletion mutant indicated a defect in 60S biogenesis which was nearly fully reversed ..

Null mutants of XRN1, encoding the major cytoplasmic exoribonuclease in yeast, are viable but accumulate decapped, deadenylated transcripts...

..XRN1 (SKI1) encodes a cytoplasmic 5'-exoribonuclease responsible for the majority of cytoplasmic RNA turnover, whereas SKI2, ..

..Here, we will discuss the recent, and often surprising, advances in our understanding of ribosome synthesis in the yeast Saccharomyces cerevisiae. These will underscore the unexpected complexity of eukaryotic ribosome synthesis...

..e., increased secretion of killer toxin activity by strains carrying the killer genome. These genes are designated ski1 through ski4 (for superkiller), ski3 and ski4 are located on chromosome XIV, and ski1 is on chromosome VII...

..Understanding these pathways and how they are integrated with other cellular pathways will provide the intellectual underpinning for investigators carrying out translational research. ..

..Two models accounting for these results are that this complex is required for normal 60S function or that this complex acts in a 3'-mRNA degradation pathway. Experiments will be carried out to distinguish between these two models. ..

..cerevisiae as a model system. The focus is on the XRN1 gene, encoding the major 5'-3' exoribonuclease activity of yeast and believed to be the major catabolic enzyme in ..

..3) Determine the function of Arx1 p and Reilp, two functionally related proteins that act at the polypeptide exit tunnel on the nascent large ribosomal subunit during export and as it enters the cytoplasmic pool of active subunits. ..