ABSTRACT
During the post-transcriptional events of the HIV-2 replication cycle, the full-length unspliced genomic RNA (gRNA) is first used as an mRNA to synthesize Gag and Gag-Pol proteins and then packaged into progeny virions. However, the mechanisms responsible for the coordinate usage of the gRNA during these two mutually exclusive events are poorly understood. Here, we present evidence showing that HIV-2 expression induces stress granule assembly in cultured cells. This contrasts with HIV-1, which interferes with stress granules assembly even upon induced cellular stress. Moreover, we observed that the RNA-binding protein and stress granules assembly factor TIAR associates with the gRNA to form a TIAR-HIV-2 ribonucleoprotein (TH2RNP) complex localizing diffuse in the cytoplasm or aggregated in stress granules. Although the assembly of TH2RNP in stress granules did not require the binding of the Gag protein to the gRNA, we observed that increased levels of Gag promoted both translational arrest and stress granule assembly. Moreover, HIV-2 Gag also localizes to stress granules in the absence of a 'packageable' gRNA. Our results indicate that the HIV-2 gRNA is compartmentalized in stress granules in the absence of active translation prior to being selected for packaging by the Gag polyprotein.
Subject(s)
Cytoplasmic Granules/virology , HIV-2/genetics , RNA, Viral/metabolism , Virus Assembly , Cytoplasmic Granules/metabolism , Eukaryotic Initiation Factor-2/metabolism , Genome, Viral , HIV-2/physiology , HeLa Cells , Humans , Protein Biosynthesis , RNA, Viral/analysis , RNA, Viral/biosynthesis , RNA-Binding Proteins/chemistry , RNA-Binding Proteins/metabolism , Ribonucleoproteins/metabolism , Stress, Physiological , Virus Replication , gag Gene Products, Human Immunodeficiency Virus/biosynthesis , gag Gene Products, Human Immunodeficiency Virus/geneticsABSTRACT
The small mRNA (SmRNA) of all Bunyaviridae encodes the nucleocapsid (N) protein. In 4 out of 5 genera in the Bunyaviridae, the smRNA encodes an additional nonstructural protein denominated NSs. In this study, we show that Andes hantavirus (ANDV) SmRNA encodes an NSs protein. Data show that the NSs protein is expressed in the context of an ANDV infection. Additionally, our results suggest that translation initiation from the NSs initiation codon is mediated by ribosomal subunits that have bypassed the upstream N protein initiation codon through a leaky scanning mechanism.
Subject(s)
Hantavirus Infections/virology , Orthohantavirus/genetics , Peptide Chain Initiation, Translational , RNA, Viral/genetics , Viral Nonstructural Proteins/genetics , Cell Line , Gene Expression Regulation, Viral , Orthohantavirus/metabolism , Humans , Open Reading Frames , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Viral/metabolism , Viral Nonstructural Proteins/metabolismABSTRACT
In the process of translation of eukaryotic mRNAs, the 5' cap and the 3' poly(A) tail interact synergistically to stimulate protein synthesis. Unlike its cellular counterparts, the small mRNA (SmRNA) of Andes hantavirus (ANDV), a member of the Bunyaviridae, lacks a 3' poly(A) tail. Here we report that the 3' untranslated region (3'UTR) of the ANDV SmRNA functionally replaces a poly(A) tail and synergistically stimulates cap-dependent translation initiation from the viral mRNA. Stimulation of translation by the 3'UTR of the ANDV SmRNA was found to be independent of viral proteins and of host poly(A)-binding protein.