Use of Cellular Decapping Activators by Positive-Strand RNA Viruses

Jungfleisch, Jennifer; Blasco-Moreno, Bernat; Díez, Juana

doi:10.3390/v8120340

Cited by 8 publications

(7 citation statements)

References 75 publications

(95 reference statements)

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“…The Lsm1 protein is part of the complex of cellular mRNA decapping activators employed by positive-strand RNA viruses to promote their translation and replication (reviewed in Jungfleisch et al, 2016) and might stabilize orthopoxviral mRNAs containing 5′ poly(A) leaders (Bergman et al, 2007). Despite many similarities between poxviral and pGKL-encoded transcription and RNA-modification apparatuses (Jeske et al, 2007), the simplest explanation for the increased pGKL toxin production in the K. lactis lsm1 Δ strain might be the stabilization of pGKL mRNAs in the absence of Lsm1p due to prominent involvement of the Lsm1 protein in a cytoplasmic deadenylation-dependent mRNA decay pathway (reviewed in Parker, 2012).…”

Section: Resultsmentioning

confidence: 99%

Messenger RNAs of Yeast Virus-Like Elements Contain Non-templated 5′ Poly(A) Leaders, and Their Expression Is Independent of eIF4E and Pab1

et al. 2019

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We employed virus-like elements (VLEs) pGKL1,2 from Kluyveromyces lactis as a model to investigate the previously neglected transcriptome of the broader group of yeast cytoplasmic linear dsDNA VLEs. We performed 5′ and 3′ RACE analyses of all pGKL1,2 mRNAs and found them not 3′ polyadenylated and containing frequently uncapped 5′ poly(A) leaders that are not complementary to VLE genomic DNA. The degree of 5′ capping and/or 5′ mRNA polyadenylation is specific to each gene and is controlled by the corresponding promoter region. The expression of pGKL1,2 transcripts is independent of eIF4E and Pab1 and is enhanced in lsm1Δ and pab1Δ strains. We suggest a model of primitive pGKL1,2 gene expression regulation in which the degree of 5′ mRNA capping and 5′ non-template polyadenylation, together with the presence of negative regulators such as Pab1 and Lsm1, play important roles. Our data also support a hypothesis of a close relationship between yeast linear VLEs and poxviruses.

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Section: Resultsmentioning

confidence: 99%

Messenger RNAs of Yeast Virus-Like Elements Contain Non-templated 5′ Poly(A) Leaders, and Their Expression Is Independent of eIF4E and Pab1

et al. 2019

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“…The increased toxin production by the slow-growing K. lactis IFO1267 pbp1Δ pab1Δ strain was more noticeable when toxin production to the culture medium was quantified as the diameter of the inhibition zone on the lawn of the sensitive yeast strain per production cell (Figs. 7A, S1) The Lsm1 protein is part of the complex of cellular mRNA decapping activators employed by positive-strand viruses to promote their translation and replication (reviewed in (124)) and might stabilize orthopoxviral mRNAs containing 5' poly(A) leaders (39). Despite the many similarities between poxviruses and the apparatuses of pGKL transcription and RNA modification (22), the simplest explanation for increased pGKL toxin production in the lsm1Δ strain might be the stabilization of pGKL mRNAs in the cell due to prominent involvement of the Lsm1 protein in a cytoplasmic deadenylation-dependent mRNA decay pathway (reviewed in (125)).…”

Section: Pab1 and Lsm1 Deletions Support The Translation Of Pgkl Mrnasmentioning

confidence: 99%

Messenger RNAs transcribed from yeast linear cytoplasmic plasmids possess unconventional 5’ and 3’ UTRs and suggest a novel mechanism of translation

Vopálenský

Sýkora

Mašek

et al. 2018

Preprint

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Linear plasmids with almost identical compact genetic organization have been found in the cytoplasm of yeast species from nine genera. We employed pGKL1,2 plasmids from Kluyveromyces lactis as a model to investigate the previously unstudied transcriptome of yeast cytoplasmic linear plasmids. We performed 5' and 3' RACE analysis of all the pGKL1,2 mRNAs and found them not 3' polyadenylated and containing mostly uncapped 5' poly(A) leaders that are not complementary to the plasmid DNA. The degree of 5' capping and/or 5' polyadenylation is specific to each gene and is controlled by the corresponding promoter regions. We refined the description of the pGKL1,2 promoters and found new alternative promoters of several genes. We also provide evidence that K2ORF3 encodes an mRNA cap guanine-N 7 -methyltransferase and that 5' capped pGKL1,2 transcripts contain N 7 -methylated caps. Translation of pGKL1,2 transcripts is enhanced in lsm1Δ and pab1Δ strains and is independent of eIF4E and Pab1 translation factors. We suggested a model of a primitive regulation of pGKL1,2 plasmids gene expression where degree of 5' mRNA capping, degree of 5' non-template polyadenylation and presence of negative regulators as PAB1 and Lsm1 play an important role. Our data also suggest a close relationship between linear plasmids and poxviruses. doi: bioRxiv preprint 4 synthesized in a template-independent manner. We show that plasmid promoters directly determine the formation of the mRNA 5' end leaders and their capping, pointing to a possible role of the plasmid RNA polymerase in this unusual phenomenon. We also provide the first evidence that MTase is an essential part of the K2Orf3p enzyme and that capped pGKL mRNAs are methylated at the N 7 position of the terminal guanosine moiety. Using in vitro and in vivo approaches, we demonstrate that translation of plasmid-specific mRNAs is independent of major cellular cap-binding proteins, translation initiation factor 4E (eIF4E), and the Pab1 and Lsm1 proteins that were speculated to be possible translational enhancers and/or stabilizers of cellular and viral mRNAs bearing 5' poly(A) stretches (38,39). Our results thus suggest the existence of a novel translation initiation mechanism. Materials and Methods General Strategy for the Modification of pGKL Plasmids Using Homologous Recombination In VivoK. lactis IFO1267 was transformed with a PCR-generated fragment consisting of 5' and 3' ends homologous to the part of the pGKL plasmid to be modified, a non-homologous part that introduces mutation/s into a plasmid-specific protein coding sequence, and a gene encoding a resistance marker (typically against G418 or hygromycin B) whose transcription is driven by the UCR of K1ORF1 or K1ORF2. This type of construct was prepared by fusion PCR; for the organization of such a construct, see Fig. 2A. After transformation, yeast cells were plated onto selective agar media, and their DNA content was analyzed for the presence of the modified pGKL plasmid using agarose electrophoresis. Both modified and wild-type t...

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“…It appears that the positive effect of the complex on viral translation requires its RNA‐binding activity, but how this mediates BMV RNA circularization to facilitate translation is not clear. Regarding replication, at least four positive strand viruses infecting plants, insects and humans rely on the Pat1/Lsm1‐7 complex (Jungfleisch et al ); reviewed (Jungfleisch et al )). Interestingly, the bacterial Lsm1 homologue, Hfq, which forms hexameric rings, has been characterized as the host factor for RNA bacteriophage Qb replication.…”

Section: Introductionmentioning

confidence: 99%

Pat1 RNA‐binding proteins: Multitasking shuttling proteins

2019

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Post-transcriptional regulation of gene expression is largely achieved at the level of splicing in the nucleus, and translation and mRNA decay in the cytosol. While the regulation may be global, through the direct inhibition of central factors, such as the spliceosome, translation initiation factors and mRNA decay enzymes, in many instances transcripts bearing specific sequences or particular features are regulated by RNA-binding factors which mobilize or impede recruitment of these machineries. This review focuses on the Pat1 family of RNA-binding proteins, conserved from yeast to man, that enhance the removal of the 5 0 cap by the decapping enzyme Dcp1/2, leading to mRNA decay and also have roles in translational repression. Like Dcp1/2, other decapping coactivators, including DDX6 and Edc3, and translational repressor proteins, Pat1 proteins are enriched in cytoplasmic P-bodies, which have a principal role in mRNA storage. They also concentrate in nuclear Cajalbodies and splicing speckles and in man, impact splice site choice in some pre-mRNAs. Pivotal to these functions is the association of Pat1 proteins with distinct heptameric Lsm complexes: the cytosolic Pat1/Lsm1-7 complex mediates mRNA decay and the nuclear Pat1/Lsm2-8 complex alternative splicing. This dual role of human Pat1b illustrates the power of paralogous complexes to impact distinct processes in separate compartments. The review highlights our recent findings that Pat1b mediates the decay of AU-rich mRNAs, which are particularly enriched in P-bodies, unlike the decapping activator DDX6, which acts on GC-rich mRNAs, that tend to be excluded from P-bodies, and discuss the implications for mRNA decay pathways. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNRNA Processing > Splicing Regulation/Alternative Splicing Translation > Translation Regulation K E Y W O R D S3 0 -5 0 decay, 5 0 -3 0 decay, alternative splicing, deadenylation, RNA processing

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Use of Cellular Decapping Activators by Positive-Strand RNA Viruses

Cited by 8 publications

References 75 publications

Messenger RNAs of Yeast Virus-Like Elements Contain Non-templated 5′ Poly(A) Leaders, and Their Expression Is Independent of eIF4E and Pab1

Messenger RNAs of Yeast Virus-Like Elements Contain Non-templated 5′ Poly(A) Leaders, and Their Expression Is Independent of eIF4E and Pab1

Messenger RNAs transcribed from yeast linear cytoplasmic plasmids possess unconventional 5’ and 3’ UTRs and suggest a novel mechanism of translation

Pat1 RNA‐binding proteins: Multitasking shuttling proteins

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