The reovirus mutant tsA279 has temperature-sensitive lesions in the M2 and L2 genes: the M2 gene is associated with decreased viral protein production and blockade in transmembrane transport.
Temperature-sensitive mutants provide an ideal means for dissecting viral assembly pathways. The morphological variants produced by and biological characteristics of tsA279, a previously uncharacterized mutant from the Fields' panel of temperature-sensitive mutants of reovirus, were determined under restrictive growth conditions. The mutant showed a distinctive pattern of increased temperature sensitivity as the temperature was raised from 39 degrees to 40 degrees. Wild-type reovirus type 1 Lang and the mutant were crossed to generate reassortants. Efficiency of plating analyses of the reassortants showed that tsA279 has temperature-sensitive lesions in two genes, a mildly temperature-sensitive one in L2, which encodes core spike protein lambda 2, and a stronger, dominant lesion in M2, which encodes major outer capsid protein mu 1. Electron microscopic examination of thin-sectioned tsA279-infected cells showed three ways in which the mutant phenotypes were expressed. The mutant appeared to be blocked in transmembrane transport of virions, a phenotype that mapped to the M2 gene; the mutant produced significantly reduced amounts of identifiable particles; and those particles that were produced appeared to be morphological variants. Immunofluorescent microscopy and immunoprecipitations of tsA279- and various T1L x tsA279 reassortant-infected cells suggested that the reduction in observed progeny was caused by a decreased production of viral proteins at the nonpermissive temperature. This phenotype also mapped to the mutant M2 gene.
Hazelton
P R
PR
Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, Canada.
Coombs
K M
KM
D000818:Animals; D002213:Capsid / Q000235:genetics*; D036022:Capsid Proteins; D002462:Cell Membrane / Q000821:virology; D011992:Endosomes / Q000821:virology; D005814:Genes, Viral / Q000235:genetics*; D007181:Inclusion Bodies, Viral / Q000648:ultrastructure; D007739:L Cells / Q000821:virology; D012089:Mammalian orthoreovirus 3 / Q000235:genetics* / Q000502:physiology; D051379:Mice; D009154:Mutation / Q000502:physiology*; D009713:Nucleotidyltransferases; D015388:Organelles / Q000821:virology; D018165:Orthoreovirus / Q000235:genetics / Q000502:physiology; D016865:Reassortant Viruses / Q000235:genetics / Q000502:physiology; D013696:Temperature; D014758:Viral Core Proteins / Q000235:genetics*; D014764:Viral Proteins / Q000096:biosynthesis; D015678:Viral Structural Proteins / Q000235:genetics*; D014779:Virus Replication
D036022:Capsid Proteins; D014758:Viral Core Proteins; D014764:Viral Proteins; D015678:Viral Structural Proteins; C055356:mu1 protein, Reovirus; C071342:reovirus protein lambda2; D009713:Nucleotidyltransferases