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Fine mapping of mutations in the fusion-inducing MP strain of herpes simplex virus type 1
Abstract:
Previous studies [W. T. Ruyechan, L. S. Morse, D. M. Knipe, and B. Roizman (1979) J. Virol. 29, 677-697] have shown that multiple mutations are responsible for the mutant phenotypes of herpes simplex virus type 1, strain MP, and have indicated that these mutations may be located on the genome between map coordinates 0.70 and 0.83. Strain MP produces large syncytial (Syn) plaques on many cell types and does not express glycoprotein C (gC-), whereas a sibling strain mP produces wild-type, small, nonsyncytial (Syn+) plaques and is gC+. Cloned DNA fragments from strains MP and mP (and strain F) were used in marker transfer and marker rescue experiments to map more precisely the mutations in MP. It was found that a 680-bp fragment from MP DNA (map coordinates 0.735 to 0.740) could transfer a Syn marker to mP and that, conversely, an overlapping fragment from mP DNA (map coordinates 0.728 to 0.744) could rescue the Syn mutation of MP. Recombinant viruses obtained in these experiments differed from the donor of the cloned DNA fragment in plaque size, however, indicating that mutation(s) at other regions of the MP genome cause enlarged plaques, in which the infected cells are less rounded than in wild-type plaques. A fragment of MP DNA from map coordinates 0.60 to 0.64 transferred a mutation causing the gC- phenotype to strain mP, and a fragment of F DNA from map coordinates 0.62 to 0.64 rescued the gC- mutation of MP. These results, coupled with data published by Frink et al. [(1983) J. Virol. 45, 643-467], indicate that the mutation responsible for the gC- phenotype of MP may be in the structural gene for gC.
Insights
Herpes simplex virus type 1 (HSV-1) strain MP mutations affecting syncytial plaque formation and glycoprotein C expression were precisely mapped. A mutation for gC- was located in the gC structural gene.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Herpes simplex virus type 1 (HSV-1) strain MP exhibits distinct phenotypes: large syncytial (Syn) plaques and lack of glycoprotein C (gC-) expression.
- Previous studies localized potential mutations for these phenotypes to the HSV-1 genome between map coordinates 0.70 and 0.83.
Purpose of the Study:
- To precisely map the mutations responsible for the syncytial plaque formation and gC- phenotype in HSV-1 strain MP.
- To identify the specific genetic regions and genes involved in these HSV-1 mutant phenotypes.
Main Methods:
- Utilized marker transfer and marker rescue experiments with cloned DNA fragments from HSV-1 strains MP, mP, and F.
- Employed specific DNA fragments to transfer or rescue mutations related to syncytial plaque formation and gC- expression.
Main Results:
- A 680-bp fragment (map coordinates 0.735-0.740) from MP DNA transferred the Syn marker to mP, while an overlapping mP fragment (0.728-0.744) rescued the MP Syn mutation.
- Recombinant viruses showed plaque size variations, suggesting additional mutations influence the Syn phenotype.
- A DNA fragment (0.60-0.64) from MP transferred the gC- phenotype to mP, and a fragment from strain F (0.62-0.64) rescued the MP gC- mutation, indicating the gC- mutation is likely within the gC structural gene.
Conclusions:
- Precisely mapped mutations responsible for syncytial plaque formation and gC- expression in HSV-1 strain MP.
- The mutation causing the gC- phenotype in strain MP is strongly suggested to reside within the structural gene for glycoprotein C.