High molecular weight RNAs and small interfering RNAs induce systemic posttranscriptional gene silencing in plants

Plant immunity against foreign gene invasion takes advantage of posttranscriptional gene silencing (PTGS). How plants elaborately avert inappropriate PTGS of endogenous coding genes remains unclear. We demonstrate in Arabidopsis that both 5′-3′ and 3′-5′ cytoplasmic RNA decay pathways act as repressors of transgene and endogenous PTGS. Disruption of bidirectional cytoplasmic RNA decay leads to pleiotropic developmental defects and drastic transcriptomic alterations, which are substantially rescued by PTGS mutants. Upon dysfunction of bidirectional RNA decay, a large number of 21- to 22-nucleotide endogenous small interfering RNAs are produced from coding transcripts, including multiple microRNA targets, which could interfere with their cognate gene expression and functions. This study highlights the risk of unwanted PTGS and identifies cytoplasmic RNA decay pathways as safeguards of plant transcriptome and development.

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Posttranscriptional gene silencing in nuclei

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1009805108 ◽

2010 ◽

Vol 108 (1) ◽

pp. 409-414 ◽

Cited By ~ 49

Author(s):

Paul Hoffer ◽

Sergey Ivashuta ◽

Olga Pontes ◽

Alexa Vitins ◽

Craig Pikaard ◽

...

Keyword(s):

Gene Silencing ◽

Target Genes ◽

Rna Degradation ◽

Small Interfering Rnas ◽

Double Stranded Rna ◽

Posttranscriptional Gene Silencing ◽

Subcellular Compartmentation ◽

Specific Degradation ◽

Precursor Mrna ◽

Specific Sequences

In plants, small interfering RNAs (siRNAs) with sequence homology to transcribed regions of genes can guide the sequence-specific degradation of corresponding mRNAs, leading to posttranscriptional gene silencing (PTGS). The current consensus is that siRNA-mediated PTGS occurs primarily in the cytoplasm where target mRNAs are localized and translated into proteins. However, expression of an inverted-repeat double-stranded RNA corresponding to the soybeanFAD2-1Adesaturase intron is sufficient to silenceFAD2-1, implicating nuclear precursor mRNA (pre-mRNA) rather than cytosolic mRNA as the target of PTGS. SilencingFAD2-1using intronic or 3′-UTR sequences does not affect transcription rates of the target genes but results in the strong reduction of target transcript levels in the nucleus. Moreover, siRNAs corresponding to pre-mRNA–specific sequences accumulate in the nucleus. In Arabidopsis, we find that two enzymes involved in PTGS, Dicer-like 4 and RNA-dependent RNA polymerase 6, are localized in the nucleus. Collectively, these results demonstrate that siRNA-directed RNA degradation can take place in the nucleus, suggesting the need for a more complex view of the subcellular compartmentation of PTGS in plants.

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Small Interfering RNAs That Trigger Posttranscriptional Gene Silencing Are Not Required for the Histone H3 Lys9 Methylation Necessary for Transgenic Tandem Repeat Stabilization in Neurospora crassa

Molecular and Cellular Biology ◽

10.1128/mcb.25.9.3793-3801.2005 ◽

2005 ◽

Vol 25 (9) ◽

pp. 3793-3801 ◽

Cited By ~ 36

Author(s):

Agustin Chicas ◽

Emma C. Forrest ◽

Silvia Sepich ◽

Carlo Cogoni ◽

Giuseppe Macino

Keyword(s):

Gene Silencing ◽

Neurospora Crassa ◽

Chromatin Immunoprecipitation ◽

Histone H3 ◽

Transcriptional Gene Silencing ◽

Small Interfering Rnas ◽

Posttranscriptional Gene Silencing ◽

Endogenous Gene ◽

Homologous Genes ◽

Interfering Rna

ABSTRACT In Neurospora crassa, the introduction of a transgene can lead to small interfering RNA (siRNA)-mediated posttranscriptional gene silencing (PTGS) of homologous genes. siRNAs can also guide locus-specific methylation of Lys9 of histone H3 (Lys9H3) in Schizosaccharomyces pombe. Here we tested the hypothesis that transgenically derived siRNAs may contemporaneously both activate the PTGS mechanism and induce chromatin modifications at the transgene and the homologous endogenous gene. We carried out chromatin immunoprecipitation using a previously characterized albino-1 (al-1) silenced strain but detected no alterations in the pattern of histone modifications at the endogenous al-1 locus, suggesting that siRNAs produced from the transgenic locus do not trigger modifications in trans of those histones tested. Instead, we found that the transgenic locus was hypermethylated at Lys9H3 in our silenced strain and remained hypermethylated in the quelling defective mutants (qde), further demonstrating that the PTGS machinery is dispensable for Lys9H3 methylation. However, we found that a mutant in the histone Lys9H3 methyltransferase dim-5 was unable to maintain PTGS, with transgenic copies being rapidly lost, resulting in reversion of the silenced phenotype. These results indicate that the defect in PTGS of the Δdim-5 strain is due to the inability to maintain the transgene in tandem, suggesting a role for DIM-5 in stabilizing such repeated sequences. We conclude that in Neurospora, siRNAs produced from the transgenic locus are used in the RNA-induced silencing complex-mediated PTGS pathway and do not communicate with an RNAi-induced initiation of transcriptional gene silencing complex to effect chromatin-based silencing.

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The Coat Protein of Turnip Crinkle Virus Suppresses Posttranscriptional Gene Silencing at an Early Initiation Step

Journal of Virology ◽

10.1128/jvi.77.1.511-522.2003 ◽

2003 ◽

Vol 77 (1) ◽

pp. 511-522 ◽

Cited By ~ 218

Author(s):

Feng Qu ◽

Tao Ren ◽

T. Jack Morris

Keyword(s):

Coat Protein ◽

Gene Silencing ◽

Rna Silencing ◽

Rna Degradation ◽

Plant Viruses ◽

Early Initiation ◽

Turnip Crinkle Virus ◽

Small Interfering Rnas ◽

Posttranscriptional Gene Silencing ◽

Initiation Step

ABSTRACT Posttranscriptional gene silencing (PTGS), or RNA silencing, is a sequence-specific RNA degradation process that targets foreign RNA, including viral and transposon RNA for destruction. Several RNA plant viruses have been shown to encode suppressors of PTGS in order to survive this host defense. We report here that the coat protein (CP) of Turnip crinkle virus (TCV) strongly suppresses PTGS. The Agrobacterium infiltration system was used to demonstrate that TCV CP suppressed the local PTGS as strongly as several previously reported virus-coded suppressors and that the action of TCV CP eliminated the small interfering RNAs associated with PTGS. We have also shown that the TCV CP must be present at the time of silencing initiation to be an effective suppressor. TCV CP was able to suppress PTGS induced by sense, antisense, and double-stranded RNAs, and it prevented systemic silencing. These data suggest that TCV CP functions to suppress RNA silencing at an early initiation step, likely by interfering the function of the Dicer-like RNase in plants.

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The epigenetic factor FVE orchestrates cytoplasmic SGS3-DRB4-DCL4 activities to promote transgene silencing in Arabidopsis

Science Advances ◽

10.1126/sciadv.abf3898 ◽

2021 ◽

Vol 7 (32) ◽

pp. eabf3898

Author(s):

Di Sun ◽

Yanjun Li ◽

Zeyang Ma ◽

Xingxing Yan ◽

Niankui Li ◽

...

Keyword(s):

Gene Silencing ◽

Small Interfering Rnas ◽

Loss Of Function ◽

Double Stranded Rna ◽

Posttranscriptional Gene Silencing ◽

Epigenetic Factor ◽

Dsrna Binding ◽

Dsrna Binding Protein

Posttranscriptional gene silencing (PTGS) is a regulatory mechanism to suppress undesired transcripts. Here, we identified Flowering locus VE (FVE), a well-known epigenetic component, as a new player in cytoplasmic PTGS. Loss-of-function fve mutations substantially reduced the accumulation of transgene-derived small interfering RNAs (siRNAs). FVE interacts with suppressor of gene silencing 3 (SGS3), a master component in PTGS. FVE promotes SGS3 homodimerization that is essential for its function. FVE can bind to single-stranded RNA and double-stranded RNA (dsRNA) with moderate affinities, while its truncated form FVE-8 has a significantly increased binding affinity to dsRNA. These affinities affect the association and channeling of SGS3-RNA to downstream dsRNA binding protein 4 (DRB4)/Dicer-like protein 2/4 (DCL2/4) complexes. Hence, FVE, but not FVE-8, biochemically enhances the DRB4/DCL2/4 activity in vitro. We surmise that FVE promotes production of transgene-derived siRNAs through concertedly tuning SGS3-DRB4/DCL2/4 functions. Thus, this study revealed a noncanonical role of FVE in PTGS.

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Defective Interfering RNA Hinders the Activity of a Tombusvirus-Encoded Posttranscriptional Gene Silencing Suppressor

Journal of Virology ◽

10.1128/jvi.79.1.450-457.2005 ◽

2005 ◽

Vol 79 (1) ◽

pp. 450-457 ◽

Cited By ~ 42

Author(s):

Zoltán Havelda ◽

Csaba Hornyik ◽

Anna Válóczi ◽

József Burgyán

Keyword(s):

Gene Silencing ◽

Viral Infections ◽

Rna Viruses ◽

Helper Virus ◽

Small Interfering Rnas ◽

Posttranscriptional Gene Silencing ◽

Virus Rna ◽

Defective Interfering Rna ◽

Interfering Rna

ABSTRACT Defective interfering (DI) RNAs are subviral replicons originating from the viral genome and are associated with many plant RNA viruses and nearly all animal RNA viruses. The presence of DI RNAs in tombusvirus-infected plants reduces the accumulation of helper virus RNA and results in the development of attenuated symptoms similar to those caused by tombusviruses defective in p19, the posttranscriptional gene silencing (PTGS) suppressor. In situ analysis of infected plants containing DI RNAs revealed that the extent of virus infection was spatially restricted as was found for p19-defective tombusvirus. Previously, p19 was shown to suppress PTGS by sequestering the small interfering RNAs (siRNAs), which act as the specificity determinant for PTGS. Our results demonstrate that DI RNAs dramatically elevate the level of virus-specific siRNAs in viral infections, resulting in the saturation of p19 and the accumulation of unbound siRNAs. Moreover, we showed that, at low temperature, where PTGS is inhibited, DI RNAs are not able to efficiently interfere with virus accumulation and protect the plants. These data show that the activation of PTGS plays a pivotal role in DI RNA-mediated interference. Our data also support a role for 21-nucleotide siRNAs in PTGS signaling.

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Microtubule motors and other maps

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015753x ◽

1990 ◽

Vol 48 (3) ◽

pp. 1-1

Author(s):

Richard B. Vallee

Keyword(s):

Molecular Weight ◽

High Molecular Weight ◽

Cytoplasmic Dynein ◽

Organelle Transport ◽

Structural Components ◽

Microtubule Associated Proteins ◽

Microtubule Motors ◽

Associated Proteins ◽

The Subject ◽

Intracellular Motility

Microtubules are involved in a number of forms of intracellular motility, including mitosis and bidirectional organelle transport. Purified microtubules from brain and other sources contain tubulin and a diversity of microtubule associated proteins (MAPs). Some of the high molecular weight MAPs - MAP 1A, 1B, 2A, and 2B - are long, fibrous molecules that serve as structural components of the cytamatrix. Three MAPs have recently been identified that show microtubule activated ATPase activity and produce force in association with microtubules. These proteins - kinesin, cytoplasmic dynein, and dynamin - are referred to as cytoplasmic motors. The latter two will be the subject of this talk.Cytoplasmic dynein was first identified as one of the high molecular weight brain MAPs, MAP 1C. It was determined to be structurally equivalent to ciliary and flagellar dynein, and to produce force toward the minus ends of microtubules, opposite to kinesin.

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Abstract #462 Acute Hypercortisolism Associated with Fractionated Radiotherapy to a Corticotroph Macroadenoma Initially Suspected to be Producing High Molecular Weight ACTH Molecule

Endocrine Practice ◽

10.1016/s1530-891x(20)46806-5 ◽

2019 ◽

Vol 25 ◽

pp. 224-225

Author(s):

Divya Akshintala ◽

Sreevidya Subbarayan

Keyword(s):

Molecular Weight ◽

High Molecular Weight ◽

Fractionated Radiotherapy

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Antioxidant activity of the high-molecular-weight (HMW) phenolic fraction of pecans

Planta Medica ◽

10.1055/s-0036-1596846 ◽

2016 ◽

Vol 81 (S 01) ◽

pp. S1-S381

Author(s):

P Greenspan ◽

MB Kellett ◽

RB Pegg

Keyword(s):

Molecular Weight ◽

Antioxidant Activity ◽

High Molecular Weight ◽

Phenolic Fraction

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Studies on the Functionality of Newly Synthesized Fibrinogen after Treatment of Acute Myocardial Infarction with Streptokinase, Increase in the Rate of Fibrinopeptide Release

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649710 ◽

1993 ◽

Vol 70 (06) ◽

pp. 0978-0983 ◽

Cited By ~ 7

Author(s):

Edelmiro Regano ◽

Virtudes Vila ◽

Justo Aznar ◽

Victoria Lacueva ◽

Vicenta Martinez ◽

...

Keyword(s):

Myocardial Infarction ◽

Acute Myocardial Infarction ◽

Molecular Weight ◽

Steady State ◽

High Molecular Weight ◽

Coronary Arteries ◽

Risk Index ◽

Weight Fraction ◽

High Molecular Weight Fraction ◽

Fibrinopeptide A

SummaryIn 15 patients with acute myocardial infarction who received 1,500,000 U of streptokinase, the gradual appearance of newly synthesized fibrinogen and the fibrinopeptide release during the first 35 h after SK treatment were evaluated. At 5 h the fibrinogen circulating in plasma was observed as the high molecular weight fraction (HMW-Fg). The concentration of HMW-Fg increased continuously, and at 20 h reached values higher than those obtained from normal plasma. HMW-Fg represented about 95% of the total fibrinogen during the first 35 h. The degree of phosphorylation of patient fibrinogen increased from 30% before treatment to 65% during the first 5 h, and then slowly declined to 50% at 35 h.The early rates of fibrinopeptide A (FPA) and phosphorylated fibrinopeptide A (FPAp) release are higher in patient fibrinogen than in isolated normal HMW-Fg and normal fibrinogen after thrombin addition. The early rate of fibrinopeptide B (FPB) release is the same for the three fibrinogen groups. However, the late rate of FPB release is higher in patient fibrinogen than in normal HMW-Fg and normal fibrinogen. Therefore, the newly synthesized fibrinogen clots faster than fibrinogen in the normal steady state.In two of the 15 patients who had occluded coronary arteries after SK treatment the HMW-Fg and FPAp levels increased as compared with the 13 patients who had patent coronary arteries.These results provide some support for the idea that an increased synthesis of fibrinogen in circulation may result in a procoagulant tendency. If this is so, the HMW-Fg and FPAp content may serve as a risk index for thrombosis.

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