Blocks to herpes simplex virus type 1 replication in a cell line, tsBN2, encoding a temperature-sensitive RCC1...

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Herpes simplex virus type 1 (HSV-1) genome circularization is a key early event in its lytic cycle.
• Previous research suggested Regulator of Chromatin Condensation 1 (RCC1) is essential for HSV-1 genome circularization and DNA synthesis.

Purpose of the Study:

• To re-examine the role of RCC1 in HSV-1 genome circularization and replication using the tsBN2 cell line.
• To investigate the specific stages of HSV-1 replication affected by RCC1 deficiency.

Main Methods:

• Infection of tsBN2 cells (carrying a temperature-sensitive RCC1 mutation) with wild-type HSV-1 and a derivative enabling circularization visualization.
• Analysis of viral DNA synthesis, concatemer cleavage, capsid protein expression, and beta-galactosidase production under permissive and non-permissive conditions.
• Temperature-upshift experiments to determine the timing of RCC1's role.

Main Results:

• Absence of functional RCC1 reduced but did not abolish HSV-1 genome circularization and viral DNA synthesis.
• No infectious progeny virus was produced in RCC1-deficient cells.
• Impaired concatemer cleavage and late-stage capsid protein expression were observed.
• RCC1's role was confirmed at later stages (>6 h post-infection) via temperature-upshift experiments.
• Reduced beta-galactosidase expression suggested potential defects in nuclear genome delivery or early gene expression.

Conclusions:

• Functional RCC1 is required for efficient HSV-1 genome circularization and DNA synthesis.
• RCC1 plays a critical role in late stages of HSV-1 replication, including concatemer processing and capsid formation.
• RCC1 may also influence early events such as nuclear entry or initial gene expression of HSV-1.