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Characterization of human malaria parasite Plasmodium falciparum eIF4E homologue and mRNA 5′ cap status

ABSTRACT: The mRNA 5′ cap is normally essential for eukaryotic mRNA translation, stabilization and transport and both the cap and eIF4E are important elements of post-transcriptional gene regulation. To further our understanding of mRNA translation in the human malaria parasite Plasmodium falciparum, we have investigated the parasite translation initiation factor eIF4E and its interaction with 5′ capped mRNA. We have purified P. falciparum eIF4E as a recombinant protein and demonstrated that it has canonical mRNA 5′ cap binding activity. We used this protein to purify P. falciparum full-length 5′ capped mRNAs from total parasite RNA. Microarray analysis comparing total and eIF4E-purified 5′ capped mRNAs shows that a subset of 34 features were more than two-fold under-represented in the purified RNA sample, including 19 features representative of nuclear transcripts. The uncapped nuclear transcripts may represent a class of mRNAs targeted for storage and cap removal. Keywords: total RNA vs purified capped mRNA

ORGANISM(S): Plasmodium falciparum

PROVIDER: GSE6356 | GEO | 2007/07/07

SECONDARY ACCESSION(S): PRJNA99563

REPOSITORIES: GEO

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Characterization of human malaria parasite Plasmodium falciparum eIF4E homologue and mRNA 5â² cap status

Project description:The mRNA 5â² cap is normally essential for eukaryotic mRNA translation, stabilization and transport and both the cap and eIF4E are important elements of post-transcriptional gene regulation. To further our understanding of mRNA translation in the human malaria parasite Plasmodium falciparum, we have investigated the parasite translation initiation factor eIF4E and its interaction with 5â² capped mRNA. We have purified P. falciparum eIF4E as a recombinant protein and demonstrated that it has canonical mRNA 5â² cap binding activity. We used this protein to purify P. falciparum full-length 5â² capped mRNAs from total parasite RNA. Microarray analysis comparing total and eIF4E-purified 5â² capped mRNAs shows that a subset of 34 features were more than two-fold under-represented in the purified RNA sample, including 19 features representative of nuclear transcripts. The uncapped nuclear transcripts may represent a class of mRNAs targeted for storage and cap removal. Keywords: total RNA vs purified capped mRNA The microarray data were obtained from four hybridizations using RNA from two independent GST-PfeIF4E purifications from separate malaria cultures.

2010-06-10 | E-GEOD-6356 | biostudies-arrayexpress

Hypermethylated capped selenoprotein mRNAs in mammals

Project description:Mammalian mRNAs are generated by complex and coordinated biogenesis pathways and acquire 5'-end m7G caps that play fundamental roles in processing and translation. Here we show that several selenoprotein mRNAs are not recognized efficiently by translation initiation factor eIF4E because they bear a hypermethylated cap. This cap modification is acquired via a 5M-bM-^@M-^Yend maturation pathway similar to that of the small nucle(ol)ar RNAs (sn- and snoRNAs). Our findings also establish that the trimethylguanosine synthase 1 (Tgs1) interacts with selenoprotein mRNAs for cap hypermethylation and that assembly chaperones and core proteins devoted to sn- and snoRNP maturation contribute to recruiting Tgs1 to selenoprotein mRNPs. We further demonstrate that the hypermethylated-capped selenoprotein mRNAs localize to the cytoplasm, are associated with polysomes and thus translated. Moreover, we found that the activity of Tgs1, but not of eIF4E, is required for the synthesis of the GPx1 selenoprotein in vivo. In total 7 samples; 3 control IP (HeLa 1,2 & 9), 2 TGS1-SF IP(C2 & C2b) and 2 TGS1-LF IP(C7 & C7b)

2014-05-14 | E-GEOD-57625 | biostudies-arrayexpress

Hypermethylated capped selenoprotein mRNAs in mammals

Project description:Mammalian mRNAs are generated by complex and coordinated biogenesis pathways and acquire 5'-end m7G caps that play fundamental roles in processing and translation. Here we show that several selenoprotein mRNAs are not recognized efficiently by translation initiation factor eIF4E because they bear a hypermethylated cap. This cap modification is acquired via a 5’end maturation pathway similar to that of the small nucle(ol)ar RNAs (sn- and snoRNAs). Our findings also establish that the trimethylguanosine synthase 1 (Tgs1) interacts with selenoprotein mRNAs for cap hypermethylation and that assembly chaperones and core proteins devoted to sn- and snoRNP maturation contribute to recruiting Tgs1 to selenoprotein mRNPs. We further demonstrate that the hypermethylated-capped selenoprotein mRNAs localize to the cytoplasm, are associated with polysomes and thus translated. Moreover, we found that the activity of Tgs1, but not of eIF4E, is required for the synthesis of the GPx1 selenoprotein in vivo.

2014-05-14 | GSE57625 | GEO

hCLE/RTRAF-HSPC117-DDX1-FAM98B: A new cap-binding complex that activates mRNA translation

Project description:hCLE/C14orf166/RTRAF, DDX1 and HSPC117 are components of cytoplasmic mRNA-transporting granules kinesin-associated in dendrites. They have also been found in cytoplasmic ribosome-containing RNA granules that transport specific mRNAs halted for translation until specific neuronal signals renders them accessible to the translation machinery. hCLE associates to DDX1, HSPC117 and FAM98B in HEK293T cells and all four proteins bind to cap analog-containing resins. Competition and elution experiments indicate that binding of hCLE complex to cap resins is independent of eIF4E; the cap-binding factor needed for translation. Purified hCLE free of its associated proteins binds cap with low affinity suggesting that its interacting proteins modulate its cap association. hCLE silencing reduces hCLE accumulation and that of its interacting proteins and decreases mRNA translation. hCLE-associated RNAs have been isolated and sequenced; RNAs involved in mRNA translation are specifically associated. The data suggest a positive role of hCLE complex modulating mRNA translation.

2019-02-18 | GSE84824 | GEO

The RNA NAD+ cap is widespread in the Arabidopsis transcriptome and probably promotes translation

Project description:As the most common mRNA cap, the m7G cap impacts the fate of an mRNA in eukaryotes. The metabolite and redox agent, nicotinamide adenine diphosphate (NAD+), can be used as an initiating nucleotide in RNA synthesis to result in NAD+-capped RNAs. Such RNAs have been identified in bacteria, yeast, and human cells, but it is not known whether they exist in plant transcriptomes. The functions of the NAD+ cap in RNA metabolism or translation are still poorly understood. Here, through NAD captureSeq, we show that NAD+- capped RNAs are widespread in Arabidopsis thaliana. NAD+-capped RNAs are predominantly messenger RNAs encoded by the nuclear and mitochondrial genomes but not the chloroplast genome. NAD-capped transcripts from the nuclear genome appear to be spliced and polyadenylated. Furthermore, although NAD+-capped transcripts constitute a small proportion of the total transcript pool from any gene, they are enriched in the polysomal fraction and associate with translating ribosomes. Our findings implicate the existence of as yet unknown mechanisms of translation initiation on NAD+-capped mRNAs. More importantly, our findings suggest that cellular metabolic and/or redox states may influence, and maybe regulated by, mRNA NAD capping.

2019-06-03 | GSE127002 | GEO

Epigenetic activation of a subset of mRNAs identified using polyribosome microarray analysis

Project description:Background: Translation deregulation is an important mechanism that causes aberrant cell growth, proliferation and survival. eIF4E, the mRNA 5 prime cap–binding protein, plays a major role in translational control. To understand how eIF4E affects cellular proliferation and cell survival, we identified mRNA targets that are translationally responsive to eIF4E. Methodology/ principal findings: Microarray analysis of polysomal mRNA from an eIF4E-inducible NIH 3T3 cell line was performed. Induction of eIF4E expression resulted in increased translation of a defined set of mRNAs; many of the mRNAs are novel targets, including those that encode large- and small-subunit ribosomal proteins and cell growth–related factors. eIF4E overexpression also led to augmented translation of mRNAs encoding anti-apoptotic proteins, which conferred resistance to endoplasmic reticulum–mediated apoptosis. Conclusions/ significance: Our results shed new light on the mechanisms by which eIF4E prevents apoptosis and transforms cells. Downregulation of eIF4E and its downstream targets is a therapeutic option for the development of novel anti-cancer drugs. Keywords: time course

2007-04-21 | GSE6639 | GEO

Discovery of a novel plant eIF4E-binding protein: Conserved Binding of eIF4E 1 (CBE1)

Project description:Regulation of translation initiation is accomplished in diverse eukaryotes through proteins which bind to the mRNA cap-binding protein, eIF4E, and either prevent its association with eIF4G or form repressive mRNPs which exclude the translation machinery. Such mechanisms in plants, and even the presence of eIF4E-interacting proteins outside of eIF4G (and the plant-specific isoform eIFiso4G, which binds eIFiso4E) which operate in a gene regulatory manner are not known. Here we describe the Conserved Binding of eIF4E 1 (CBE1), a plant-specific protein with an evolutionarily conserved eIF4E binding motif. This protein binds eIF4E or eIFiso4E in vitro to form cap-binding complexes, and is found as a constituent of cap-binding complexes in vivo in an eIF4E-dependent manner. Mutants lacking CBE1 show dysregulation of cell cycle related transcripts, accumulating higher levels relative to wild-type plants of mRNAs encoding proteins involved in mitotic processes. These findings support CBE1 as a plant protein with the capability to form cap-binding complexes with the potential for gene regulatory activity.

2018-09-26 | GSE114363 | GEO

Landscape of RNA NAD+ capping in Arabidopsis unopened flower bud

Project description:Eukaryotic messenger RNAs (mRNAs) possess a 5’-end N7-methyl guanosine (m7G) cap that promotes their translation and stability. However, it was recently demonstrated that eukaryotic mRNAs can also carry a 5' end nicotinamide adenine dinucleotide (NAD+) cap that promotes mRNA decay mediated by the NAD+ decapping enzyme DXO1. However, the dynamic regulation of NAD+ capping in plant remains unknown. Here, we describe the global landscape of NAD+-capped RNAs in Arabidopsis thaliana, and demonstrate that DXO1 is responsible for removal of these 5’-end modifications and facilitates mRNA degradation in plant transcriptomes. We also reveal that in the absence of DXO1 NAD+-capped mRNAs are unstable and processed into smRNAs. Furthermore, we find that Abscisic Acid (ABA) remodel the landscape of RNA cap epitransciptome, and the mRNA lost their NAD+ cap contribute to their stability under ABA. Overall, our results support a link between ABA response and RNA NAD+ capping.

2020-11-23 | GSE142389 | GEO

Landscape of RNA NAD+ capping in Arabidopsis seedling with ABA treatment

2020-11-23 | GSE142388 | GEO

2'-O-methylation of the second transcribed nucleotide in eukaryotic RNA 5’ cap impacts protein production levels and susceptibility to DXO-mediated transcript degradation

Project description:Eukaryotic mRNA 5’ end is decorated with cap structure which plays multiple roles in the cell. Most importantly, protects transcript from exonucleolytic degradation and enables translation of encoded protein conducted by cap-dependent machinery. This is also a key feature in the process of recognizing RNA as self or non-self molecule by cellular innate immune system. Cap is composed of 7-methylguanosine linked by a 5′,5′-triphosphate chain to the first transcribed nucleotide, and is formed enzymatically during transcription. This m7GpppN structure, called cap0, can be further modified by CMTR1 methyltransferase to cap1 (m7GpppNm), which predominates in eukaryotic cells. Cap2, with additional 2′-O-methylation at the second transcribed nucleotide (m7GpppNmpNm) added by another methyltransferase CMTR2, also can be found at mRNA 5’ end. We present new tools allowing for in vitro synthesis of RNAs possessing cap2, i.e tetranucleotide cap analogues. Utilizing these for in vitro transcription reactions we obtained RNAs with 2′-O-methylation present at the second transcribed nucleotide. Due to that we investigated the role of cap2 in protein production from reporter mRNA protected with this structure in different conditions, normal or stress ones, or with CMTR1/2 down regulated level. We also assessed the affinity of eIF4E protein to differentially capped RNAs. Furthermore, we verified whether an additional 2′-O-methylation presence in capped RNA makes transcript more resistant to decapping enzyme action.

2022-09-08 | PXD028636 | Pride

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