Effect of Small Polyanions on In Vitro Assembly of Selected Members of Alpha-, Beta- and Gammaretroviruses.

Alžběta Dostálková,Tomáš Ruml,Filip Kaufman,Michaela Rumlová,Barbora Vokatá,Pavel Ulbrich

doi:10.3390/v13010129

Abstract

The assembly of a hexameric lattice of retroviral immature particles requires the involvement of cell factors such as proteins and small molecules. A small, negatively charged polyanionic molecule, myo-inositol hexaphosphate (IP6), was identified to stimulate the assembly of immature particles of HIV-1 and other lentiviruses. Interestingly, cryo-electron tomography analysis of the immature particles of two lentiviruses, HIV-1 and equine infectious anemia virus (EIAV), revealed that the IP6 binding site is similar. Based on this amino acid conservation of the IP6 interacting site, it is presumed that the assembly of immature particles of all lentiviruses is stimulated by IP6. Although this specific region for IP6 binding may be unique for lentiviruses, it is plausible that other retroviral species also recruit some small polyanion to facilitate the assembly of their immature particles. To study whether the assembly of retroviruses other than lentiviruses can be stimulated by polyanionic molecules, we measured the effect of various polyanions on the assembly of immature virus-like particles of Rous sarcoma virus (RSV), a member of alpharetroviruses, Mason-Pfizer monkey virus (M-PMV) representative of betaretroviruses, and murine leukemia virus (MLV), a member of gammaretroviruses. RSV, M-PMV and MLV immature virus-like particles were assembled in vitro from truncated Gag molecules and the effect of selected polyanions, myo-inostol hexaphosphate, myo-inositol, glucose-1,6-bisphosphate, myo-inositol hexasulphate, and mellitic acid, on the particles assembly was quantified. Our results suggest that the assembly of immature particles of RSV and MLV was indeed stimulated by the presence of myo-inostol hexaphosphate and myo-inositol, respectively. In contrast, no effect on the assembly of M-PMV as a betaretrovirus member was observed.

Highlights

Retroviruses assemble immature particles either in the cytosol or at the plasma membrane of the host cell
It was thought that the assembly of retroviral immature particles is stimulated predominantly by protein–protein and protein–nucleic acid interactions of CA–CA and NC
An increasing amount of evidence, shows that interactions of proteins with small molecules take an essential place in the stimulation of retroviral hexameric lattice formation

Summary

Introduction

Retroviruses assemble immature particles either in the cytosol or at the plasma membrane of the host cell. Mouse mammary tumor virus (MMTV), are representatives of the morphological type. D, which assembles intracytoplasmic A-type particles (ICAPs) in the pericentriolar region. ICAPs are transported to the plasma membrane where budding and maturation occur. In the cytosol [1,2] This complex is transported to the plasma membrane, where the. Gag molecules multimerize to form immature particles. The processes of budding and maturation are similar for immature particles of both D type and C type. Immature particles of all retroviruses are composed of radially arranged Gag polyprotein precursors, which assemble into a hexagonal lattice [3,4,5,6]. Gag contains three major domains common to all retroviruses: matrix (MA), capsid (CA), and nucleocapsid (NC)

Methods

Results

Conclusion