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A negative-sense single strand RNA virus (or (-)ssRNA virus) is a virus that uses negative sense RNA as its genetic material. Single stranded RNA viruses are classified as positive or negative depending on the sense or polarity of the RNA. The negative viral RNA is complementary to the mRNA and must be converted to a positive RNA by RNA polymerase before transcription. Therefore, the purified RNA of a negative sense virus is not infectious by itself, as it needs to be converted to a positive sense RNA for replication. The virus belongs to Group V on the Baltimore classification. ==Replication== Negative sense ssRNA virus needs RNA polymerase to form a positive sense RNA. The positive sense RNA acts as a viral mRNA, which is translated into proteins for the production of new virion materials. With the newly formed virions, more negative sense RNA molecules are produced. In more details, replication of the virus consists of the following steps: # A virion enters the host cell and releases its negative RNA into the cytoplasm. # The virus uses its own RNA replicase, also known as RNA-dependent RNA polymerase (RdRp), to form positive RNA template strands through complementary base pairing. # The positive RNA acts as mRNA, which is translated into structural capsomere proteins and viral RdRp by the host's ribosomes. # A replicative complex is formed with RdRp: The positive strands can either function as mRNA to produce more proteins or as template to make more negative RNA strands. # New viral capsids are assembled with the capsomere proteins. The negative RNA strands combine with capsids and viral RdRp to form new negative RNA virions. # After assembly and maturation of nucleocapsid, the new virions exit the cell by budding or lysing through cell membrane to further infect other cells. The genome size of a negative RNA virus is between 10kb to 30kb. Two genome subgroups can be distinguished, nonsegmented and segmented, and are described as such: *In viruses with nonsegmented genomes, the first step of replication is transcription of the negative strand by RdRp to form various monocistronic mRNA that code for individual viral proteins. A positive strand copy is formed to serve as template for the production of the negative genome. This replication takes place in the cytoplasm. *In viruses with segmented genomes, replication occurs in the nucleus and the RdRp produces one monocistronic mRNA strand from each genome segment. The principal difference between the two types is the location of replication. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Negative-sense single strand RNA virus」の詳細全文を読む スポンサード リンク
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