''Brome mosaic virus'' (BMV) is a small (28
nm, 86S), positive-stranded,
icosahedral RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohyd ...
plant virus
Plant viruses are viruses that affect plants. Like all other viruses, plant viruses are obligate intracellular parasites that do not have the molecular machinery to replicate without a host. Plant viruses can be pathogenic to higher plants.
M ...
belonging to the genus ''
Bromovirus'', family ''
Bromoviridae
''Bromoviridae'' is a family of viruses
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bac ...
'', in the ''
Alphavirus
''Alphavirus'' is a genus of RNA viruses, the sole genus in the ''Togaviridae'' family. Alphaviruses belong to group IV of the Baltimore classification of viruses, with a positive-sense, single-stranded RNA genome. There are 32 alphaviruses, w ...
''-like superfamily.
BMV was first isolated in 1942 from bromegrass (''Bromus inermis''),
had its
genomic
Genomics is an interdisciplinary field of biology focusing on the structure, function, evolution, mapping, and editing of genomes. A genome is an organism's complete set of DNA, including all of its genes as well as its hierarchical, three-dim ...
organization determined by the 1970s, and was completely sequenced with commercially available
clones by the 1980s.
The alphavirus-like superfamily includes more than 250 plant and animal viruses including
Tobacco mosaic virus
''Tobacco mosaic virus'' (TMV) is a positive-sense single-stranded RNA virus species in the genus '' Tobamovirus'' that infects a wide range of plants, especially tobacco and other members of the family Solanaceae. The infection causes character ...
,
Semliki forest virus
The Semliki Forest virus is an alphavirus found in central, eastern, and southern Africa. It was first isolated from mosquitoes in the Semliki Forest, Uganda by the Uganda Virus Research Institute in 1942 and described by Smithburn and Haddow. ...
,
Hepatitis E virus
The hepatitis E virus (HEV) is the causative agent of hepatitis E. It is of the species ''Orthohepevirus A.''
Globally, approximately 939 million corresponding to 1 in 8 individuals have ever experienced HEV infection. About 15–110 million ind ...
,
Sindbis virus
''Sindbis virus'' (SINV) is a member of the ''Togaviridae'' family, in the ''Alphavirus'' genus. The virus was first isolated in 1952 in Cairo, Egypt. The virus is transmitted by mosquitoes ('' Culex'' and Culiseta). SINV is linked to Pogosta ...
, and
arbovirus
Arbovirus is an informal name for any virus that is transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...
es (which cause certain types of
encephalitis
Encephalitis is inflammation of the brain. The severity can be variable with symptoms including reduction or alteration in consciousness, headache, fever, confusion, a stiff neck, and vomiting. Complications may include seizures, hallucinations, ...
).
[Sullivan & Ahlquist, 1997] Many of the positive-strand RNA viruses that belong to the
alphavirus
''Alphavirus'' is a genus of RNA viruses, the sole genus in the ''Togaviridae'' family. Alphaviruses belong to group IV of the Baltimore classification of viruses, with a positive-sense, single-stranded RNA genome. There are 32 alphaviruses, w ...
family share a high degree of similarity in proteins involved in genomic replication and synthesis. The sequence similarities of RNA replication
genes
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
and strategies for BMV have been shown to extend to a wide range of plant and animal viruses beyond the alphaviruses, including many other positive-strand RNA viruses from other families.
Understanding how these viruses replicate and targeting key points in their life cycle can help advance antiviral treatments worldwide.
Genome
BMV has a
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gen ...
that is divided into three
5' cap
In molecular biology, the five-prime cap (5′ cap) is a specially altered nucleotide on the 5′ end of some primary transcripts such as precursor messenger RNA. This process, known as mRNA capping, is highly regulated and vital in the creation ...
ped RNAs. RNA1 (3.2 kb) encodes a protein called 1a (109 kDa), which contains both an N-proximal
methyltransferase
Methyltransferases are a large group of enzymes that all methylate their substrates but can be split into several subclasses based on their structural features. The most common class of methyltransferases is class I, all of which contain a Ross ...
domain and a C-proximal
helicase
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating ...
-like domain. The methyltransferase domain shows sequence similarity to other alphavirus m7G methyltransferases and guanyltransferases, called nsP1 proteins, involved in RNA capping. RNA2 (2.9 kb) encodes the 2a protein (94 kDa), the RNA-dependent RNA polymerase, responsible for replication of the viral genome.
[ The dicistronic RNA3 (2.1 kb) encodes for two proteins, the 3a protein (involved in cell-to-cell migration during infection) and the coat protein (for RNA ]