Intracellular topology and epitope shielding of poliovirus 3A protein

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• The poliovirus RNA replication complex is crucial for viral propagation.
• Viral proteins 3A and 3AB are key players in poliovirus replication, membrane rearrangement, and polymerase anchoring.
• The precise localization and accessibility of protein 3A during infection are not fully understood.

Purpose of the Study:

• To investigate the accessibility of the amino-terminal epitope of poliovirus protein 3A during viral infection.
• To determine the role of the viral RNA-dependent RNA polymerase in the shielding of protein 3A.

Main Methods:

• Immunofluorescence microscopy was used to detect the 3A epitope in infected and uninfected cells.
• Differential permeabilization and proteolysis experiments were performed to assess protein localization.
• Comparisons were made between wild-type poliovirus and a temperature-sensitive mutant affecting the 3D polymerase.

Main Results:

• The amino-terminal epitope of 3A-containing proteins is significantly shielded in poliovirus-infected cells compared to cells expressing 3A alone.
• This shielding is not due to luminal orientation of the proteins.
• Shielding is more pronounced with wild-type poliovirus, suggesting polymerase involvement.

Conclusions:

• Direct binding of the poliovirus RNA-dependent RNA polymerase (3Dpol) to 3A-containing proteins likely occludes the amino terminus of 3A.
• This interaction is a key feature of the poliovirus RNA replication complex.
• Understanding this interaction provides insights into viral RNA synthesis regulation.