Link between genome packaging and rate of budding for Rous sarcoma virus

Area of Science:

• Virology and Molecular Biology
• Retroviral Assembly and RNA Packaging

Background:

• The precise subcellular location for genomic RNA packaging by Gag proteins during retrovirus assembly is not fully understood.
• The membrane-binding (M) domain of Gag is crucial for targeting to the plasma membrane, influencing the intracellular trafficking pathway and genome packaging efficiency.

Purpose of the Study:

• To investigate the relationship between Gag protein targeting to the plasma membrane and genomic RNA packaging efficiency in Rous sarcoma virus (RSV).
• To elucidate the role of the M domain and nucleocapsid (NC) domain in RSV Gag trafficking and viral particle assembly.

Main Methods:

• Construction and analysis of a Rous sarcoma virus (RSV) mutant (Super M) with altered M domain properties.
• Assessment of viral particle production, infectivity, and genomic RNA content.
• Investigation of Gag protein localization, including nuclear export pathway inhibition (CRM-1) and effects of NC domain deletion.

Main Results:

• The Super M mutant exhibited accelerated particle production but reduced infectivity and genomic RNA content.
• Super M Gag did not accumulate in the nucleus upon CRM-1 inhibition, unlike wild-type Gag.
• Deletion of the NC domain impaired plasma membrane localization of wild-type Gag but not Super M Gag, suggesting enhanced membrane targeting of Super M.

Conclusions:

• Enhanced membrane-targeting properties of the Super M mutant's Gag protein appear to inhibit efficient genome packaging.
• Restoring wild-type M domain characteristics rescued budding efficiency, genome packaging, and infectivity.
• These findings suggest an intrinsic link between Gag protein targeting and genome packaging to ensure viral RNA incorporation into RSV particles.