Uncoating of adenovirus type 2

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Adenovirus uncoating is a critical step for viral DNA delivery into the host cell nucleus.
• Understanding the precise mechanisms and intermediates of adenovirus uncoating is essential for comprehending viral replication and developing antiviral strategies.

Purpose of the Study:

• To investigate the sequential steps and intermediates involved in adenovirus type 2 uncoating.
• To elucidate the cause of non-infectivity in a temperature-sensitive mutant (tsl) of adenovirus.

Main Methods:

• Infection of HEp-2 cells with radiolabeled adenovirus type 2 and its temperature-sensitive mutant (tsl).
• Analysis of nuclear and cytoplasmic fractions using sucrose gradient velocity sedimentation and SDS-polyacrylamide gel electrophoresis.
• Kinetic and compartmentalization studies to track viral structures during uncoating.

Main Results:

• Adenovirus type 2 virions were converted into three distinct subviral structures within 1 hour of infection.
• These structures included cytoplasmic subviral particles, nuclear/cytoplasmic corelike structures (containing DNA and specific polypeptides), and nuclear DNA-terminal protein complexes.
• The DNA-terminal protein complex was identified as the likely end product of the uncoating process.
• Virions of the tsl mutant, produced at non-permissive temperatures, were blocked at the corelike stage, lacking infectivity.

Conclusions:

• A model for adenovirus uncoating is proposed, detailing the progression through distinct subviral intermediates.
• The uncoating defect in the tsl mutant, specifically the blockage at the corelike stage, explains its failure to initiate infection.
• The study identifies key viral polypeptides and their association with DNA throughout the uncoating process.