Satellites are a heterologous collection of subviral agents which comprise nucleic acid molecules that depend for their productive multiplication (replication) on a helper virus, but which contain sequences substantially distinct from those of the genomes of either their helper virus or their hosts. Satellites are thus distinct from either defective (D) or defective interfering (DI) RNAs, because the latter are wholly

Early in this century, a key aim of bacteriophage researchers was to use these viruses as antibacterial therapeutic agents. This line of investigation was discontinued due to technical difficulties and the advent of antibiotics. However, the recent proliferation of antibiotic resistant strains has revived interest in this area. Recently, investigators have described the isolation of mutants of phages A and P22 that have extended lifetimes in the murine circulatory system, and can abort experimental infections.

See also: Coliphage lambda (Siphoviridae); Lysogeny and prophage; Phage Homologous Recombination.

Further Reading

Campbell A and Botstein D (1983) Evolution of the lambdoid phages. In: Hendrix RW, Roberts JW, Stahl FW and Weisberg RA (eds) Lambda II. New York: Cold Spring Harbor Laboratory. Casjens S and Hendrix R (1988) Control mechanisms in dsDNA bacteriophage assembly. In: Calendar R (ed.) The Bacteriophages, vol. 2, New York: Plenum. King J, Haase-Pettingell C, Robinson AS, Speed M and Mitraki A (1996) Thermolabile folding intermediates: inclusion body precursors and chaperonin substrates. FASEB ] 10: 57. Poteete AR (1988) Bacteriophage P22. In: Calendar R (ed.)

The Bacteriophages, vol. 2, New York: Plenum Press. Susskind MM and Botstein D (1978) Molecular genetics of bacteriophage P22. Microbiol. Rev. 42: 385.

derived from their helper virus genomes. However, there are some hybrid RNAs between satellites and parts of the viral genome, such as the chimeric molecules formed from part of a satellite RNA associated with turnip crinkle virus (TCV) and part of a DI RNA formed from the virus genome. Satellites may encode their own coat protein (CP) (satellite viruses), or they may rely on the helper virus for encapsidation as well as replication (the satellite RNAs or satellite DNA). Satellites are not needed

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