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An association between actin and nucleocapsid polypeptides in isolated murine retroviral particles
1Medical Research Council, Laboratory of Molecular Biology, Cambridge, U.K.
Abstract:
Mammalian cells infected with retroviruses frequently display virus particles budding at the tip of cellular projections resembling microvilli and filopodia. In normal and infected cells these cellular projections contain actin microfilaments and in specialized retrovirus-tipped projections from the P815 cell, a direct association between actin filaments and the apical virus particle could be demonstrated (Mortara and Koch, 1986). Here we confirm and extend these observations using a murine macrophage cell line chronically infected with a C-type retrovirus. Immunochemical and biochemical methods were used to identify actin-associated and actin-binding components among the retroviral polypeptides. The results show that Pr65gag and its p15 N-terminal domain can bind to actin in vitro and may be major binding sites for actin filaments on the retroviral nucleocapsid.
Insights
Retrovirus budding in mammalian cells involves actin microfilaments. The retroviral Pr65gag protein and its p15 domain bind to actin, potentially anchoring virus particles to cellular projections.
Area of Science:
- Cell Biology
- Virology
- Molecular Biology
Background:
- Mammalian cells infected with retroviruses often show virus particles budding from cellular projections like microvilli and filopodia.
- These projections contain actin microfilaments, and previous studies indicated a direct association between actin filaments and budding retroviruses.
Purpose of the Study:
- To confirm and extend observations on the association between retroviral particles and actin filaments.
- To identify actin-binding components within retroviral polypeptides.
Main Methods:
- Utilized a murine macrophage cell line chronically infected with a C-type retrovirus.
- Employed immunochemical and biochemical methods to analyze retroviral polypeptides for actin association.
Main Results:
- Demonstrated that the retroviral Pr65gag protein and its N-terminal p15 domain can bind to actin in vitro.
- Identified these viral components as potential major binding sites for actin filaments on the retroviral nucleocapsid.
Conclusions:
- The findings confirm and extend the role of actin microfilaments in retroviral budding.
- The Pr65gag protein and its p15 domain are identified as key interactors with actin, mediating the association of retroviral nucleocapsids with cellular projections.