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Rhabdoviruses

	Rhabdoviruses The rhabdoviruses are usually bullet shaped viruses tbat have been found in plants, invertebrates and vertebrates. The bullet shape with one flattened end has been the subject of much discussion. It has been suggested that the particles are actually bacilliform, with both ends hemispherical. The flattening at one end may be the result of rupture, during preparation for electron microscopy, at the terminus where the budding particle is sealed. The broccoli necrosis virus is bacillus shaped, with both ends rounded. Examples of rhabdoviruses are the vesicular stomatitis virus (VSV), rabies virus, wheat striate mosaic virus and the poiato yellow dwarf virus.
The vesicular stomatitis virus, which has been particularly well studied, is a mild pathogen of cattle. The virus is covered by an envelope which consists of a lipid bilayer, on the outside of which arc numerous spikes made up of G protein. The space between the nucleocapsid- and tile lipoprotein envelope is filled by the M protein. The major protein of the nucleocapsid is the N protein. There are two minor proteins Land NS, that are associated with RNA synthesis The nucleocapsid is cylindrically coiled and consists of a single RNA molecule (40S) associated with 4.5 mµ particles of the nucleocapsid protein N. There are 34 turns in the total length on a pitch of 4.5 mµ, with 24 particles per complete turn. The core of the virus is hollow
Both a transcription system and a replication system arc involved in the VSV life cycle. The transcription system produces in RNA, while the replication system generates 40S (+) and (-) RNA. The 40S RNAs occur only as nucleocapsids, while mRNA is not found in nucleocapsids. This separation of transcription and replication is an advance over the positive strand viruses, and possibly enables the negative strand viruses to have a wide range of hosts, The RNA of the virus particle is not itself an mRNA. It is a minus strand which functions as a, template on which mRNA is synthesized. This is borne out by the fact that the RNA is not infectious, that it lacks 3'-poly(A) and that it is not capped at the 5' end. Negative strand virion RNA transcribes mRNA with the help of the enzyme transcriptase which is contained within the virio
Transcriptase activity requires all the three nucleocapsid proteins, L, NS and H. The and NS proteins appear to be required for polymerization. The RNA must be coated by the H protein before it functions as a template. Five mRNAs are transcribed, which direct the synthesis of five viral proteins. The mRNAs are thus monocistronic, and are complementary to the virion RNA. In transcribing the five mRNA molecules the transcriptase reads the genome RNA continuously from one end to the other, Itha8 been suggested that there, may be a" leader sequence" before the II protein mRNA.
	The mRNAs have a 5'2-methylguanosine containing (m7G) cap and a 3' poly (A) sequence. During replication the negative strand 40S virion RNA forms a 40S positive strand template RNA. This then forms a 403 negative strand RNA.

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Herpesviruses Herpesviruses And Their Infections Poxviruses Reoviruses Reovirus RNAs and Proteins Picornaviruses Strucures of Picornavirus During Morphogenesis Togaviruses (Arboviruses) Rhabdoviruses Proteins of the Vesicular Stomatitis Orthomyxoviruses Multiplication in RNA Viruses Rous Sarcoma Virus (RSV) Interferon

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