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Title: Arenaviridae      
ID:
PRJNA16892
description:
Description of Arenaviridae adapted from ICTVdb Virion Properties Morphology Virions consist of an envelope and a nucleocapsid. Virus capsid is enveloped. Virions are spherical to pleomorphic measuring (50-)110-130(-300) nm in diameter. The envelope surrounds probably two nucleocapsids; has surface projections. Surface projections are distinctive club-shaped peplomers that are spaced widely apart and covering evenly the surface; embedded in a lipid bilayer which is comprises surface glycoproteins (GP). Surface projections are composed of one type of protein. Surface projections are 8-10 nm long. Host ribosomes are seen inside the envelope (in varying numbers). Capsid/nucleocapsid is elongated with helical symmetry. Virions consist of two nucleocapsids. The nucleocapsid is filamentous and forming a closed circle; has a "string of beads" appearance; with a varying length with a length of 1000-1300 nm (L segment, 450-640 nm (S segment) and a width of 3-4 nm. Nucleocapsid contains a polymerase complex and a nucleoprotein complex. Nucleocapsids are organized in closed circles and display a linear array of nucleosomal subunits (when they are isolated and free of contaminating host ribosomes). Physicochemical and Physical Properties Virions have a buoyant density in CsCl of 1.19-1.2 g cm-3; sucrose of 1.17-1.18 g cm-3; amidotrizoate compounds of 1.14 g cm-3. The sedimentation coefficient is 325-500 S20w. The thermal inactivation point (TIP) is at 56°C. Under in vitro conditions virions are stable when stored at -70°C; inactivated in acid environment of pH 5.5 (and below, inactivated in alkaline environment of pH 8.5 (and above). Virions are sensitive to treatment with organic solvents (and infectivity is inactivated). The infectivity is reduced after exposure to irradiation (UV and gamma-irradiation). Nucleic Acid The Mr of the genome constitutes 2% of the virion by weight. The genome is segmented and consists of two segments of linear, negative-sense to ambisense, single-stranded RNA. The genome is transcriptional inactive. Minor species of non-genomic nucleic acid are also found in virions. The encapsidated nucleic acid is mainly of genomic origin, but virions may also contain subgenomic RNA and nucleic acid of host origin including three molecules of host rRNA (of cellular origin with sedimentation coefficients of 28S, 18S and 4-6S and three subgenomic mRNA (species presumably associated with encapsidated ribosomes) derived from genomic S RNA (for the precursor of protein N and the precursor of protein GPC), or L RNA (for the Z protein). RNA segments are not homologous. The complete genome is about 10000-11000 nucleotides long. The genome has a guanine + cytosine content of 40-45 %. The genome has a virus coded terminal protein which is circular, but not covalently closed. Nucleotide sequences at the 3'-terminus are largely complementary to similar regions on the 5' end. The 5'-end of the genome does not have cap. The 3'-terminus has conserved nucleotide sequences; in all segments and species of same genus; sequence has 19-30 nucleotides in length; in S RNA. The intergenic region has S a hairpin configuration (potential depending on virus). The multipartite genome is encapsidated, each segment in a separate nucleocapsid, and the nucleocapsids are surrounded by one envelope. Each virion contains multiple copies of the genome; often segments of the genome in non-equimolar proportions (due to frequent packaging of S RNA strands). Genome Organization and Replication Virions attach to undefined receptors to enter host cells via the endosomal route. The process of intracellular uncoating of virions occurs in the cytoplasm and the viral nucleic acid is delivered to the cell cytoplasm, the site of mRNA transcription. Transcription: Virus transcription is temporally regulated. Early genes are expressed during genome uncoating. Non-structural proteins involved in transcription. The viral genome is transcribed from the viral sense strand from the 3' end, or from the 5' end. The viral genome is transcribed by a viral RNA-dependent RNA polymerase into 2 mRNA(s) (N and L mRNA). The transcribed mRNAs are subgenomic in a viral-complementary sense. Viral mRNA(s) is/are transcribed with no overlaps; in an ambisense coding arrangement; synthesized from all RNA segments. Specific termination sequences have been identified. Termination is caused by characteristic GC-rich, strongly base-paired stem loop-structure. Coding Strategy of Segment 1: RNA-L exhibits an ambisense coding strategy. That encode(s) structural proteins. Encodes 2 structural protein(s), namely a polymerase complex (L protein, and Z protein). Structural proteins are encoded in the viral-complementary sense sequence. Coding Strategy of Segment 2: RNA-S. Exhibits an ambisense coding strategy. Contains 2 ORF(s). Encode(s) structural proteins. Encodes 2 structural protein(s). The sequence encodes GPC a glycoprotein precursor and a non-glycosylated polypeptide (N). The sequence encodes GPC. Structural proteins are encoded in the viral sense sequence. Part of sequence. Acts as a template for synthesis of viral mRNA. A non-glycosylated polypeptide. N. Translational units do not overlap. Sequence has a. Intergenic non-coding region can form hairpin configuration(s). Translation: Envelope glycoproteins. Are modified by post-translational processes. Are processed to contain complex glycans. Including proteolytic cleavage. Post-translational processes occur during transport. To the plasma membrane. The genome replicates in the cytoplasm. Genome replication involves RNA-directed RNA synthesis; occurs through a single stranded replicative intermediate involving a rolling circle mechanism. The rolling circle mechanism generates complementary intermediate forms referred to as the antigenome. The process of genome replication may involve a slippage mechanism during initiation of transcription termination signals. At an early stage, templates are involved in the sysnthesis of a full-length RNA replication. Replication in vitro is sensitive to amantadine, alpha-amanitin, glucosamine, and thiosemicarbazones. Replication cycle The virus has the ability to form gene reassortment. Gene reassortment occurs during mixed infections; involving virus of the same strain; involving virus from a different species; but not between a different; species. Reassortment includes genomic sequence segments that are diploid, or multiploid. The precursor of envelope protein is found in the infected cell cytoplasm. Viral proteins accumulate in the cytoplasm. Virions accumulate in the cell cytoplasm. Assembly and Egress: Capisd proteins assemble with viral nucleic acid to form the virion. Viruses assemble at the cell membrane. Maturation: Virions mature by budding through and by fusion with plasma membranes on the cell surface in the vicinity of ribosomes in the cytoplasm. Release: Host cells remain intact. Virus is released from host cell by budding through the cell membrane; and acquisition of an envelope. Virus is released from host cell without causing death. The virus envelope is acquired from the host cell by budding off the cell membrane and is assembled in the cytoplasm.
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landingpage: http://www.ncbi.nlm.nih.gov/bioproject/PRJNA16892
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authorization:
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abbreviation:
NCBI
homePage: http://www.ncbi.nlm.nih.gov
ID:
SCR:006472
name:
National Center for Biotechnology Information
homePage: http://www.ncbi.nlm.nih.gov/bioproject
ID:
SCR:004801
name:
NCBI BioProject