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Regulation of herpes simplex virus immediate-early gene promoters in mouse neuroblastoma cells
L M Kemp1, I H Gelman, S J Silverstein
1Department of Biochemistry, University College and Middlesex School of Medicine, London, U.K.
Abstract:
The non-permissivity of C1300 mouse neuroblastoma cells for herpes simplex virus (HSV) infection is due to a failure of such cells to transcribe the immediate-early (IE) genes following viral infection. We have transfected both C1300 cells and permissive cells with constructs in which each of the 5 IE promoters drives expression of the readily assayable chloramphenicol acetyl transferase (CAT) gene. These experiments show that the lack of IE gene transcription in C1300 cells is due to the weak activity of the five IE promoters in these cells compared to that observed in a range of permissive cell types. This effect is mediated both by up-stream elements and by sequences present in the minimal promoter. The different effects of DNA concentration on the activities of the minimal and complete promoters suggests that the up-stream sequences act by binding a repressor factor present in C1300 cells whilst the weak activity of the minimal promoter results from the absence of a positive factor in such cells.
Insights
C1300 mouse neuroblastoma cells resist herpes simplex virus (HSV) due to weak transcription of viral immediate-early (IE) genes. This results from altered promoter activity, influenced by repressor and positive factors in these non-permissive cells.
Area of Science:
- Virology
- Molecular Biology
- Cell Biology
Background:
- Herpes simplex virus (HSV) infection requires transcription of immediate-early (IE) genes.
- C1300 mouse neuroblastoma cells are non-permissive to HSV, indicating a block in early viral gene expression.
Purpose of the Study:
- To investigate the molecular basis for the non-permissivity of C1300 cells to HSV.
- To determine if promoter activity of HSV IE genes is altered in C1300 cells.
Main Methods:
- Transfection of C1300 and permissive cells with constructs linking HSV IE promoters to the chloramphenicol acetyl transferase (CAT) reporter gene.
- Assaying CAT gene expression to measure IE promoter activity.
Main Results:
- HSV IE promoters exhibit significantly weaker activity in C1300 cells compared to permissive cell lines.
- Both upstream elements and minimal promoter sequences contribute to the reduced IE gene transcription.
- Evidence suggests a repressor factor binds upstream elements in C1300 cells, while a positive factor is absent for minimal promoter activity.
Conclusions:
- The non-permissivity of C1300 cells to HSV is attributed to the intrinsic weak activity of viral IE promoters in these cells.
- Host cell factors, including a repressor and the absence of a positive factor, modulate HSV IE promoter function in neuroblastoma cells.