Characterization of a new adenovirus type 5 assembly intermediate

Area of Science:

• Molecular Biology
• Virology
• Cell Biology

Background:

• Adenovirus type 5 (Ad5) is a significant human pathogen.
• Understanding viral DNA replication and assembly is crucial for developing antiviral strategies.

Purpose of the Study:

• To characterize the molecular complexes involved in Ad5 DNA replication and virion assembly.
• To investigate the potential for coupled DNA replication and packaging during adenovirion formation.

Main Methods:

• Extraction of Ad5 DNA-protein complexes from infected HeLa cells using ammonium sulphate.
• Analysis of molecular populations via centrifugation through discontinuous sucrose gradients in heavy water.
• Electron microscopy to visualize viral DNA-protein complexes and assembly intermediates.

Main Results:

• Identified distinct molecular populations: mature DNA-protein complexes, replication complexes, assembly intermediates, and virions.
• Observed assembly intermediates with partially packaged DNA, including double-stranded (ds) DNA and single-stranded (ss) DNA coated with E-72 K DNA binding protein.
• Detected Ad5 replicating DNA molecules partially packaged within capsids, with ongoing replication at one end and packaging at the other.

Conclusions:

• The observed structures suggest that virus DNA enters pre-formed capsids or precursors as an early step in assembly.
• The simultaneous replication and packaging of DNA in intermediates points to a potential coupled DNA replication-packaging process in adenovirion formation.