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Fine structure physical map locations of alterations that affect cell fusion in herpes simplex virus type 1
Abstract:
Fine structure physical map locations were determined for syncytial mutants (MP, syn-20, syn-102, syn-103, and syn-105) of Herpes Simplex Virus type 1 (HSV-1). All except MP were derived from the KOS strain. MP contains multiple mutations, including one that leads to the loss of accumulation of glycoprotein gC (Ruyechan et al., J. Virol. 29, 677-697, 1979). Overlapping DNA subclones within the prototypic map coordinates 0.707 to 0.810 were constructed from a library of KOS fragments. These were used along with intact mutant DNA to rescue the syn marker. Mutations in all of the mutants were rescued by KOS DNA sequences between 0.732 and 0.745. This cell-dependent syn mutation is the only lesion in the KOS-derived mutants. A second syn mutation in MP was mapped at coordinates 0.745 to 0.753. This lesion produces less fusion and is also cell-type dependent for the fusion phenotype. Cell-type independent fusion requires the presence of both mutations. The locus determining glycoprotein C (gC) production in strain MP was also mapped, using indirect immunofluorescence, to coordinates 0.745 to 0.753. Nucleotide sequences for ICP-27, an immediate early or alpha protein of unknown function, are within these coordinates. Since gC production and the syn phenotype are separable by recombination, they must be caused by independent mutations.
Insights
Researchers mapped syncytial (syn) mutations in Herpes Simplex Virus type 1 (HSV-1). They identified specific DNA regions responsible for cell fusion and glycoprotein C production, revealing independent genetic causes for these HSV-1 traits.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Herpes Simplex Virus type 1 (HSV-1) causes various infections.
- Syncytial (syn) mutants of HSV-1 exhibit altered cell-to-cell fusion properties.
- Understanding the genetic basis of HSV-1 virulence factors like syncytial mutations is crucial.
Purpose of the Study:
- To determine the fine structure physical map locations of syncytial mutations in HSV-1.
- To identify the specific viral genes and DNA regions responsible for the syncytial phenotype and glycoprotein C (gC) production.
Main Methods:
- Construction of overlapping DNA subclones from a library of HSV-1 KOS strain fragments.
- Rescue of syncytial mutations using these DNA subclones and intact mutant DNA.
- Mapping of mutations using recombination analysis and indirect immunofluorescence for glycoprotein C detection.
Main Results:
- Syncytial mutations in KOS-derived mutants were mapped to DNA sequences between 0.732 and 0.745, causing cell-dependent fusion.
- A second syncytial mutation in the MP strain was mapped to 0.745 to 0.753, affecting fusion and being cell-type dependent.
- The locus for glycoprotein C (gC) production in MP was mapped to 0.745 to 0.753, overlapping with the ICP-27 gene region.
- Recombination analysis demonstrated that gC production and the syncytial phenotype are caused by independent mutations.
Conclusions:
- The study successfully mapped multiple syncytial mutations in HSV-1, pinpointing specific DNA regions.
- Cell-type dependent and independent syncytial phenotypes are linked to distinct genetic loci.
- Glycoprotein C production and syncytial fusion are genetically separable traits in HSV-1, indicating independent mutations control these functions.