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MDA5 variants trade antiviral activity for protection from autoimmune disease.

Loss-of-function variants in MDA5, a key sensor of double-stranded RNA from viruses and retroelements, have been associated with protection from type 1 diabetes (T1D) in genome-wide association studies (GWAS). MDA5 loss-of-function variants have also been reported to increase the risk of inflammatory bowel disease (IBD). Whether these associations are linked or extend to other diseases remains unclear. Here, fine-mapping analysis of four large GWAS datasets shows that T1D-protective loss-of-function MDA5 variants also protect against psoriasis and hypothyroidism, while increasing the risk of IBD. The degree of autoimmune protection and IBD risk were linearly proportional. The magnitudes of the odds ratios for autoimmune protection and IBD risk were larger for rare MDA5 variants than for common variants, which were differentially expressed in different geographic populations. Our analysis suggests MDA5 genetic variants offer a direct fitness trade-off between viral clearance and autoimmune tissue damage.

Interferon-Induced Helicase, IFIH1↗

Nuclear factor kappa B: an oxidative stress-responsive transcription factor of eukaryotic cells (a review).

NF-kappa B is a multiprotein complex that can activate a great variety of genes involved in early defence reactions of higher organisms. In nonstimulated cells, NF-kappa B resides in the cytoplasm in an inactive complex with the inhibitor I kappa B. Pathogenic stimuli cause release of I kappa B and allow NF-kappa B to enter the nucleus, bind to DNA control elements and, thereby, induce the synthesis of mRNA. A puzzling feature of NF-kappa B is that its activation is triggered by a great variety of agents. These include the cytokines interleukin-1 and tumor necrosis factor, viruses, double-stranded RNA, endotoxins, phorbol esters, UV light and ionizing radiation. We recently found that also low concentrations of H2O2 activate NF-kappa B and that various antioxidants prevent the induction by H2O2. Subsequent analysis revealed that antioxidants not only suppress the activation of NF-kappa B by H2O2 but by all other inducers tested so far. In this review, we will discuss the evidences that NF-kappa B is an oxidative stress-responsive transcription factor of higher eukaryotic cells.

Animals↗

Report of a rotavirus outbreak in an adult nursing home population.

UNLABELLED: Rotavirus is a double-stranded RNA enteric virus that is the most important cause of severe, dehydrating diarrhea in infants and young children worldwide. Symptoms range from mild diarrhea to a life-threatening illness. Rotavirus occasionally afflicts adult members of the infected infant's family, geriatric patients, and immunocompromised hosts. We report the outbreak of rotavirus infection in a large nursing home facility. REPORT: In September 1996, 19 residents and 15 staff members of a 64-bed nursing home facility began to develop an acute, febrile illness associated with vomiting and diarrhea. The Public Health Service conducted an outbreak investigation. The infection displayed fecal-to-oral transmission with an incubation period of 1 to 2 days. The median duration of illness was 3 days for residents and 1 day for staff members. One resident died as a result of illness complications. Stool antigen tests from five residents and two employees were positive for rotavirus. Infection control policies were reevaluated, and interventions to arrest the outbreak were undertaken. The employee sick leave policy was strictly enforced. Education seminars were held, with employees reinforcing the concepts of enteric isolation and proper handwashing techniques. Surfaces and objects in the dining area were disinfected with a weak chloride solution. Once these measures were implemented, the rotavirus outbreak was contained. CONCLUSION: Rotavirus is a common cause of infectious diarrhea that can afflict the geriatric population. When infection occurs in a nursing home facility, rapid transmission can develop and morbidity can result. Nursing home infection control policies need to be evaluated constantly and new measures need to be implemented should an outbreak of rotavirus occur.

Journal Article↗

Differential dependence of reovirus-associated enzyme activities on genome RNA as determined by psoralen photosensitivity.

Irradiation with long wavelength UV light in the presence of 4'-substituted psoralens abolished the in fectivity of reovirus and reovirus subviral particles Photoreaction of intact virions, cores, or genome RNA resulted in the formation of psoralen monoadducts and cross-links, demonstrating that the viral genome RNA in situ is double-stranded. Virus-associated RNA polymerase activity was lost following psoralen photoreaction, consistent with dependence on the genome RNA as template for viral mRNA synthesis. By contrast, reovirus guanylyl transferase and methyl transferase activities that catalyze the formation of mRNA 5'-terminal cap, m GpppG, were relatively unaffected by photoreaction. Cations that inhibit psoralen binding to nucleic acids also protected against loss of RNA polymerase activity. Partially photoinactivated viral cores produced decreased amounts of full length viral mRNAs. The absence of prematurely terminated transcripts indicates that template RNA modification by psoralen adducts has an all-or-none effect on initiation of mRNA synthesis by the core-associated RNA polymerase.

Cations, Monovalent↗

A mode of action of RNase CI toward the various RNAs.

A mode of action of RNase CI toward the various native RNAs was examined. The mixture of tRNA from Thermus thermophilus HB8 were exhaustively cleaved by RNase CI to produce 90% of acid-soluble fraction. Among the minor nucleotides s2T were recognized by this enzyme. RNase CI generates a linear viroid molecule by introducing one single nick into viroid circular molecule. Double stranded RNA from RNA virus, such as Cytoplasmic polyhedrosis virus (CPV) from silk worm, was cleaved at some specific sites to produce more than ten of the discrete bands electrophoretically.

Animals↗

The double-stranded RNA-binding protein Staufen is incorporated in human immunodeficiency virus type 1: evidence for a role in genomic RNA encapsidation.

Human Staufen (hStau), a double-stranded RNA (dsRNA)-binding protein that is involved in mRNA transport, is incorporated in human immunodeficiency virus type 1 (HIV-1) and in other retroviruses, including HIV-2 and Moloney murine leukemia virus. Sucrose and Optiprep gradient analyses reveal cosedimentation of hStau with purified HIV-1, while subtilisin assays demonstrate that it is internalized. hStau incorporation in HIV-1 is selective, is dependent on an intact functional dsRNA-binding domain, and quantitatively correlates with levels of encapsidated HIV-1 genomic RNA. By coimmunoprecipitation and reverse transcription-PCR analyses, we demonstrate that hStau is associated with HIV-1 genomic RNA in HIV-1-expressing cells and purified virus. Overexpression of hStau enhances virion incorporation levels, and a corresponding, threefold increase in HIV-1 genomic RNA encapsidation levels. This coordinated increase in hStau and genomic RNA packaging had a significant negative effect on viral infectivity. This study is the first to describe hStau within HIV-1 particles and provides evidence that hStau binds HIV-1 genomic RNA, indicating that it may be implicated in retroviral genome selection and packaging into assembling virions.

Binding Sites↗

Coupled transcription-translation of silkworm cytoplasmic polyhedrosis virus injected into oocytes of the frog, Xenopus laevis.

The cytoplasmic polyhedrosis virus of the silkworm, Bombyx mori, contains a ten-segmented, double-stranded RNA genome and five species of polypeptides, V1 (Mr 146,000), V2 (Mr 140,000), V3 (Mr 128,000)), V4 (Mr 62,000), and V5 (Mr 32,000). The virus contains an RNA-dependent RNA polymerase that transcribes the duplex genome RNA to form mRNA either in the infected animals or under appropriate conditions in vitro. We co-microinjected the virus, [alpha-32P]GTP and actinomycin D into oocytes of the frog, Xenopus laevis, and found that at least eight species of mRNA were formed in the oocytes. Virus-injected oocytes were labeled with [35S]methionine and cell extracts were treated with rabbit anti-cytoplasmic polyhedrosis virus immunoglobulin G. Analysis of the immunoprecipitates by sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that V1, V2, and V3 were produced in the virus-injected oocytes whereas V4 and V5 were not. By injecting the separated double-stranded genome segments immediately after heat-denaturation into oocytes, it was found that V1 was coded for by segment 1 with a chain length of 4.2 kilobase pairs, V2 by segment 2 or 3, whose chain lengths are both 4.0 kilobase pairs, and V3 by segment 4 with a chain length of 3.2 kilobase pairs. These results demonstrate that the Xenopus oocyte is a very useful system for the coupled transcription-translation of double-stranded RNA viruses.

Animals↗

Molecular cloning and sequencing of the La Crosse virus S RNA.

Complete double-stranded DNA copies of the La Crosse virus (LAC) S genome have been synthesized and cloned into plasmid pBR322. The cloned genome was characterized and sequenced. The LAC S genome consisted of 981 nucleotides and contained two overlapping open reading frames. The first reading frame begins at nucleotide 82 and encodes a protein of 235 amino acids. A polypeptide of 92 amino acids can be translated in a +1 reading frame 16 nucleotides downstream from the start of the first reading frame. This second reading frame is initiated with two AUG codons followed by the serine codon UCG, the same serine codon which immediately follows the AUG of the first reading frame.

Amino Acid Sequence↗

Viruses in fungi and eukaryotic algae: their possible origins and evolution.

It now seems that isometric viruses isolated from higher fungi contain double-stranded RNA whereas those from the primitive lower fungi and eukaryotic algae possess double-stranded DNA. The possible origins and evolution of the viruses are discussed on the basis of their biological and morphological features.

Biological Evolution↗

Stability and extractability of double-stranded RNA of pangola stunt and sugarcane Fiji disease viruses in dried plant tissues.

When leaves infected with pangola stunt virus (PaSV) were dried at 23, 37, 50, 70 or 105 degrees C, the dsRNA was stable and could be extracted after aerobic storage at room temperature for 1 month, although at 105 degrees C the amount obtained was reduced. The dsRNA was also recovered after leaves were freeze dried and stored in vacuo at room temperature for 6 months, or were dried and stored aerobically at room temperature for 10.5 months. dsRNA of sugarcane Fiji disease virus (FDV) was also stable when infected leaves were dried at 23, 37, 50 or 105 degrees C and stored aerobically for 3 months or for at least 6 months when infected leaves were dried at 70 degrees C. The unexpected high stability and extractability of both PaSV and FDV dsRNA when dried in leaves at low or high temperatures and stored at room temperature indicate that these, and probably other plant-infecting reoviruses, can be transported readily in desiccated host tissue between different countries for later extraction and comparison of their dsRNAs.

Desiccation↗

The characterization and molecular cloning of the double-stranded RNA genome of an Australian strain of infectious bursal disease virus.

The genome of infectious bursal disease virus (IBDV) strain 002-73 was found to consist of two segments of double-stranded (ds) RNA which were 3400 bp (MW 2.06 X 10(6)) and 2900 bp (MW 1.76 X 10(6)) long, respectively. The ds IBDV RNA could be translated, in vitro, only after extensive denaturation. The small RNA segment was found to code for a single polypeptide of MW 90K, while the large RNA segment coded for three major polypeptides of MW 52K, 32K, and 28K, and two minor polypeptides of MW 41K and 16K. The large RNA segment could encode proteins of MW 125K while the MW of the translated products was 169K suggesting that a precursor-product relationship exists between some of the translation products. A method is described for the synthesis of ds cDNA from large ds RNA molecules. Analyses of recombinant colonies showed that inserts covering the entire IBDV genome had been cloned.

Animals↗

In vitro transcription of the double-stranded RNA genome of maize rough dwarf virus (Reoviridae).

An RNA-dependent RNA polymerase associated with particles of maize rough dwarf virus, a Fijivirus, was characterized using two in vitro assays differing in their energy regeneration systems. Optimum reaction rates occurred at pH 8.0 to 8.5 at 20 degrees C. The presence of virus and Mn2+ or Mg2+ was essential for enzyme activity; Mn2+ stimulated more incorporation events than Mg2+, at optimum concentrations of 2 to 4 mM and 4 mM, respectively. Incorporation was not affected by alpha-amanitin, actinomycin D or rifampicin. The products synthesized in vitro were single-stranded RNAs which hybridized specifically with the double-stranded genomic RNAs of five other reoviruses. The in vitro transcripts were also used to detect maize rough dwarf virus RNA in plants and in vector insects.

DNA-Directed RNA Polymerases↗

Secondary structures of influenza and Sendai Virus RNAs.

The secondary structures of influenza and Sendai virus RNAs were investigated by thermal denaturation, circular dichroism and proflavine binding methods. In 0.1 M NaCl about 60% of the bases of both RNAs were involved in secondary structure. The melting temperatures (Tm) of both viral RNAs were linear functions of the logarithm of the sodium ion concentration in solution, but under all ionic conditions the melting temperatures of Sendai virus RNA were higher than those of influenza virus RNA. At all ionic strengths the melting range of Sendai virus RNA was less than influenza virus RNA, indicating that the helical regions in Sendai virus RNA were longer than those in influenza virus RNA. Although Sendai virus RNA had a higher thermal stability than influenza virus RNA, hyperchromicity and circular dichroism data showed that Sendai virus RNA had less G+C content (34%) within the double stranded regions than influenza virus RNA (48%). The binding isotherms of Sendai and influenza virus RNA-proflavine complexes were studied at different ionic strengths. The number of binding sites of proflavine with influenza virus RNA were significantly lower than those with Sendai virus RNA. These results demonstrate the essential difference between the secondary and tertiary structures of the RNAs under study.

Base Composition↗

Single- and double-stranded viral RNAs in plants infected with the potexviruses papaya mosaic virus and foxtail mosaic virus.

Three classes of viral RNA were recovered from polyribosomes purified from papaya leaves infected with papaya mosaic virus (PapMV) and from barley leaves infected with foxtail mosaic virus (FoMV): full-length viral RNAs [6.8 and 6.2 kilobases (kb), respectively]; less abundant intermediate subgenomic RNAs (2.2 and 1.9 kb), and abundant, small subgenomic RNAs (1 and 0.9 kb). Small amounts of the PapMV-specified 1.0-kb subgenomic RNA were encapsidated, whereas no encapsidated subgenomic RNAs could be found in preparations of FoMV. Immunoprecipitation of the products of in vitro translation of the small subgenomic RNA of both viruses showed that it codes for the corresponding viral coat protein. FoMV genomic RNA isolated from polyribosomes also directed the efficient synthesis of a 37- to 38-kilodalton protein which was immunoprecipitated by an antiserum raised against the coat protein. We presume this product to be a readthrough protein initiated to the 5' side of and in the same reading frame as the coat protein-coding sequences in FoMV RNA. The predominant double-stranded viral-specified RNAs in tissues infected with PapMV, FoMV, and clover yellow mosaic virus were genome sized (6.8, 6.2, and 7.0 kb pairs, respectively). If double-stranded RNAs corresponding to coat protein subgenomic RNAs exist, they must be present in much lower relative abundances.

Genes, Viral↗