Analysis of herpes simplex virus nucleoprotein complexes extracted from infected cells

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Herpes simplex virus type 1 (HSV-1) infection involves complex interactions between viral and cellular components.
• Understanding the structure and composition of viral nucleoprotein complexes is crucial for deciphering viral replication and assembly.

Purpose of the Study:

• To characterize the nucleoprotein complexes formed during HSV-1 infection of HEp-2 cells.
• To identify the viral and cellular proteins associated with HSV-1 DNA within these complexes.

Main Methods:

• Infection of HEp-2 cells with HSV-1, labeling with [3H]thymidine and 14C-amino acids.
• Extraction and partial purification of nucleoprotein complexes using Triton X-100, NaCl, and sucrose gradient sedimentation.
• Analysis of viral DNA and proteins using CsCl isopycnic gradients, electrophoresis, and electron microscopy.
• Equilibrium centrifugation in metrizamide density gradients.

Main Results:

• A nucleoprotein complex sedimenting around 200S was isolated, containing intact viral DNA.
• Specific HSV-1 polypeptides (VP5, VP12, VP15.2, VP19, VP24) were identified in the complex, while cellular histones were absent.
• Electron microscopy revealed proteins associated with DNA ends, forming terminal thickenings or capsid-like structures, with no observed nucleosomes.
• Similar complexes were detected in the presence of phosphonoacetic acid, leading to altered nucleocapsids.

Conclusions:

• HSV-1 forms unique nucleoprotein complexes during infection, characterized by specific viral protein association with DNA.
• These complexes exhibit distinct structural features, differing from cellular nucleosomes.
• The findings provide insights into the organization of the viral genome within infected cells and potential assembly intermediates.