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Identification and mapping of the UL56 gene transcript of herpes simplex virus type 1
1Institut für Medizinische Virologie der Universität Heidelberg, F.R.G.
Abstract:
The herpes simplex virus type 1 (HSV-1) strain HFEM is apathogenic for tree shrews and mice by the intraperitoneal application route. This is due to a 4.1 kbp deletion [0.762 to 0.789 map units (mu)] within the BamHI DNA fragment B of the viral genome. With exception of 71 bp the DNA sequences of the deleted region are located within the repetitive DNA sequences of the inverted repeat of the L segment of the HSV-1 genome (IRL). A 1.5 kb RNA hybridizing to the DNA sequences of the HSV-1 genome at map position 0.760-0.762 (BssHII DNA fragment F, part of the BamHI DNA fragment B) was found to be missing in cells infected with HSV-1 HFEM and other apathogenic HSV-1 strains. A detailed analysis of the transcriptional profile of this region of the pathogenic prototype strain HSV-1 F and strand-specific hybridizations revealed that this 1.5 kb RNA species is transcribed at 2 to 4 h p.i. in leftward orientation. The corresponding open reading frame in the HSV-1 genome had been predicted as the UL56 gene. The absence of this 1.5 kb RNA in HSV-1 HFEM-infected cells is due to the fact that the promoter region of the UL56 gene is located within those DNA sequences which are deleted in the HSV-1 HFEM genome. A specific DNA fragment (650 bp) was amplified by reverse polymerase chain reaction using oligonucleotide primers corresponding to the predicted translational start and termination region of the UL56 gene. The corresponding cDNA had been derived from cellular RNA from HSV-1 F-infected cells using oligo(dT) priming. This indicates that the 1.5 kb RNA is the real transcript of the UL56 gene of HSV-1.
Insights
A herpes simplex virus type 1 (HSV-1) deletion in the UL56 gene promoter explains its apathogenicity. This missing viral RNA transcript is crucial for understanding HSV-1 virulence and developing targeted therapies.
Area of Science:
- Virology
- Molecular Biology
- Genetics
Background:
- Herpes simplex virus type 1 (HSV-1) causes various infections.
- Strain HFEM of HSV-1 is non-pathogenic in tree shrews and mice.
- A specific DNA deletion in HSV-1 HFEM is linked to its apathogenicity.
Purpose of the Study:
- To investigate the molecular basis of HSV-1 HFEM apathogenicity.
- To identify the specific viral gene and transcript affected by the deletion.
- To understand the role of the UL56 gene in HSV-1 pathogenesis.
Main Methods:
- Comparative genomic analysis of pathogenic and apathogenic HSV-1 strains.
- RNA hybridization to detect viral transcripts.
- Transcriptional profiling and strand-specific hybridization.
- Reverse transcription polymerase chain reaction (RT-PCR) to amplify specific gene transcripts.
Main Results:
- A 4.1 kbp deletion in the HSV-1 HFEM genome was identified within the inverted repeat of the L segment.
- A 1.5 kb RNA transcript, corresponding to the UL56 gene, was absent in HSV-1 HFEM-infected cells.
- The deletion encompasses the promoter region of the UL56 gene, explaining the transcript's absence.
- RT-PCR confirmed the 1.5 kb RNA as the authentic transcript of the UL56 gene.
Conclusions:
- The deletion in the UL56 gene promoter of HSV-1 HFEM is responsible for the absence of its transcript and the virus's apathogenicity.
- The UL56 gene and its transcript play a role in HSV-1 pathogenesis.
- This finding provides insights into HSV-1 virulence mechanisms and potential therapeutic targets.