Invasion gene associated RNA (InvR)
Encyclopedia
Invasion gene associated RNA (also known as InvR) is a small non-coding RNA
involved in regulating one of the major outer cell membrane
porin
proteins in Salmonella
species.
InvR was originally predicted by computational screening the genome of Salmonella typhimurium for novel sRNA genes. In this screen 46 candidate sRNA gene
s not conserved in Escherichia coli
were identified.
The Salmonella the virulence
factors that facilitate invasion of the host intestinal epithlium
are located in a ~ 40 kb region in the Salmonella genome referred to as Salmonella pathogenicity Island 1 (SPI-1). The gene encoding InvR is located in this SPI-1 region between two genes called invH and STM2901. InvR appears to be unique to Salmonella species as there does not appear to be any predicted homologues
in other Enterobacteriaceae
species.
InvR is ~80nt long and appears to be independently expressed from its own promoter. Its expression is activated by the transcription factor HilD and has been shown to be abundantly expressed during exponential growth
. InvR has been shown to bind the RNA chaperone Hfq in vitro and Hfq is required for in vivo stability. In S. typhimurium InvR RNA has been shown to repress the synthesis of the abundant outer membrane porin protein OmpD. Despite being located in the SPI-1 region there has been no link identified between the function of InvR and the SPI-1 dependent secretion pathway or invasion.
Non-coding RNA
A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...
involved in regulating one of the major outer cell membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
porin
Porin (protein)
Porins are beta barrel proteins that cross a cellular membrane and act as a pore through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules...
proteins in Salmonella
Salmonella
Salmonella is a genus of rod-shaped, Gram-negative, non-spore-forming, predominantly motile enterobacteria with diameters around 0.7 to 1.5 µm, lengths from 2 to 5 µm, and flagella which grade in all directions . They are chemoorganotrophs, obtaining their energy from oxidation and reduction...
species.
InvR was originally predicted by computational screening the genome of Salmonella typhimurium for novel sRNA genes. In this screen 46 candidate sRNA gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
s not conserved in Escherichia coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
were identified.
The Salmonella the virulence
Virulence
Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...
factors that facilitate invasion of the host intestinal epithlium
Epithelium
Epithelium is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of structures throughout the body, and also form many glands. Functions of epithelial cells include secretion, selective...
are located in a ~ 40 kb region in the Salmonella genome referred to as Salmonella pathogenicity Island 1 (SPI-1). The gene encoding InvR is located in this SPI-1 region between two genes called invH and STM2901. InvR appears to be unique to Salmonella species as there does not appear to be any predicted homologues
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
in other Enterobacteriaceae
Enterobacteriaceae
The Enterobacteriaceae is a large family of bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the...
species.
InvR is ~80nt long and appears to be independently expressed from its own promoter. Its expression is activated by the transcription factor HilD and has been shown to be abundantly expressed during exponential growth
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
. InvR has been shown to bind the RNA chaperone Hfq in vitro and Hfq is required for in vivo stability. In S. typhimurium InvR RNA has been shown to repress the synthesis of the abundant outer membrane porin protein OmpD. Despite being located in the SPI-1 region there has been no link identified between the function of InvR and the SPI-1 dependent secretion pathway or invasion.