A Bunyavirus-Inducible Ubiquitin Ligase Targets RNA Polymerase IV for Degradation during Viral Pathogenesis in Rice

San1 ubiquitin ligase is involved in nuclear protein quality control via its interaction with intrinsically disordered proteins for ubiquitylation and proteasomal degradation. Since several transcription/chromatin regulatory factors contain intrinsically disordered domains and can be inhibitory to transcription when in excess, San1 might be involved in transcription regulation. To address this, we analyzed the role of San1 in genome-wide association of TBP [that nucleates pre-initiation complex (PIC) formation for transcription initiation] and RNA polymerase II (Pol II). Our results reveal the roles of San1 in regulating TBP recruitment to the promoters and Pol II association with the coding sequences, and hence PIC formation and coordination of elongating Pol II, respectively. Consistently, transcription is altered in the absence of San1. Such transcriptional alteration is associated with impaired ubiquitylation and proteasomal degradation of Spt16 and gene association of Paf1, but not the incorporation of centromeric histone, Cse4, into the active genes in Δsan1 . Collectively, our results demonstrate distinct functions of a nuclear protein quality control factor in regulating the genome-wide PIC formation and elongating Pol II (and hence transcription), thus unraveling new gene regulatory mechanisms.

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RNA Polymerase IV Defines Epigenetic Variation in Maize

The Plant Cell ◽

10.1105/tpc.113.250310 ◽

2013 ◽

Vol 25 (3) ◽

pp. 777-777

Author(s):

Jennifer Lockhart

Keyword(s):

Rna Polymerase ◽

Epigenetic Variation ◽

Rna Polymerase Iv

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Identification of Pol IV and RDR2-dependent precursors of 24 nt siRNAs guiding de novo DNA methylation in Arabidopsis

eLife ◽

10.7554/elife.09591 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 120

Author(s):

Todd Blevins ◽

Ram Podicheti ◽

Vibhor Mishra ◽

Michelle Marasco ◽

Jing Wang ◽

...

Keyword(s):

Rna Polymerase ◽

Cytosine Methylation ◽

De Novo ◽

Transferase Activity ◽

Small Interfering Rnas ◽

Pol Iv ◽

Nuclear Rna ◽

Rna Polymerase Iv ◽

Nuclear Rna Polymerase

In Arabidopsis thaliana, abundant 24 nucleotide small interfering RNAs (24 nt siRNA) guide the cytosine methylation and silencing of transposons and a subset of genes. 24 nt siRNA biogenesis requires nuclear RNA polymerase IV (Pol IV), RNA-dependent RNA polymerase 2 (RDR2) and DICER-like 3 (DCL3). However, siRNA precursors are mostly undefined. We identified Pol IV and RDR2-dependent RNAs (P4R2 RNAs) that accumulate in dcl3 mutants and are diced into 24 nt RNAs by DCL3 in vitro. P4R2 RNAs are mostly 26-45 nt and initiate with a purine adjacent to a pyrimidine, characteristics shared by Pol IV transcripts generated in vitro. RDR2 terminal transferase activity, also demonstrated in vitro, may account for occasional non-templated nucleotides at P4R2 RNA 3’ termini. The 24 nt siRNAs primarily correspond to the 5’ or 3’ ends of P4R2 RNAs, suggesting a model whereby siRNAs are generated from either end of P4R2 duplexes by single dicing events.

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SHH1, a Homeodomain Protein Required for DNA Methylation, As Well As RDR2, RDM4, and Chromatin Remodeling Factors, Associate with RNA Polymerase IV

PLoS Genetics ◽

10.1371/journal.pgen.1002195 ◽

2011 ◽

Vol 7 (7) ◽

pp. e1002195 ◽

Cited By ~ 123

Author(s):

Julie A. Law ◽

Ajay A. Vashisht ◽

James A. Wohlschlegel ◽

Steven E. Jacobsen

Keyword(s):

Dna Methylation ◽

Rna Polymerase ◽

Chromatin Remodeling ◽

Homeodomain Protein ◽

Rna Polymerase Iv

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Elongin C Contributes to RNA Polymerase II Degradation by the Interferon Antagonist NSs of La Crosse Orthobunyavirus

Journal of Virology ◽

10.1128/jvi.02134-19 ◽

2020 ◽

Vol 94 (7) ◽

Author(s):

Andreas Schoen ◽

Simone Lau ◽

Paul Verbruggen ◽

Friedemann Weber

Keyword(s):

United States ◽

Rna Polymerase ◽

Rna Polymerase Ii ◽

Ubiquitin Ligase ◽

Nonstructural Protein ◽

E3 Ubiquitin Ligase ◽

The United States ◽

Type I ◽

La Crosse Virus ◽

Mrna Synthesis

ABSTRACT Mosquito-borne La Crosse virus (LACV; genus Orthobunyavirus, family Peribunyaviridae, order Bunyavirales) causes up to 100 annual cases of severe meningoencephalitis in children and young adults in the United States. A major virulence factor of LACV is the nonstructural protein NSs, which inhibits host cell mRNA synthesis to prevent the induction of antiviral type I interferons (IFN-α/β). To achieve this host transcriptional shutoff, LACV NSs drives the proteasomal degradation of RPB1, the large subunit of mammalian RNA polymerase II. Here, we show that NSs acts in a surprisingly rapid manner, as RPB1 degradation was commencing already at 1 h postinfection. The RPB1 degradation was partially dependent on the cellular E3 ubiquitin ligase subunit Elongin C. Consequently, removal of Elongin C, but also of the subunits Elongin A or B by siRNA transfection partially rescued general RNAP II transcription and IFN-beta mRNA synthesis from the blockade by NSs. In line with these results, LACV NSs was found to trigger the redistribution of Elongin C out of nucleolar speckles, which, however, is an epiphenomenon rather than part of the NSs mechanism. Our study also shows that the molecular phenotype of LACV NSs is different from RNA polymerase II inhibitors like α-amanitin or Rift Valley fever virus NSs, indicating that LACV is unique in involving the Elongin complex to shut off host transcription and IFN response. IMPORTANCE The mosquito-borne La Crosse virus (LACV; genus Orthobunyavirus, family Peribunyaviridae, order Bunyavirales) is prevalent in the United States and can cause severe childhood meningoencephalitis. Its main virulence factor, the nonstructural protein NSs, is a strong inhibitor of the antiviral type I interferon (IFN) system. NSs acts by imposing a global host mRNA synthesis shutoff, mediated by NSs-driven proteasomal degradation of the RPB1 subunit of RNA polymerase II. Here, we show that RPB1 degradation commences as early as 1 h postinfection, and identify the E3 ubiquitin ligase subunit Elongin C (and its binding partners Elongins A and B) as an NSs cofactor involved in RPB1 degradation and in suppression of global as well as IFN-related mRNA synthesis.

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