Project description:We analyzed the incorporation of cellular microRNAs (miRNAs) into highly purified HIV-1 virions and observed that this largely, but not entirely, mirrored the level of miRNA expression in the producer CD4+ T cells. Specifically, of the 58 cellular miRNAs detected at significant levels in the producer cells, only five miRNAs were found at a 2 to 4-fold higher level in virions than predicted based on random sampling. Of note, these included two miRNAs, miR-155 and miR-92a, reported previously to at least weakly bind HIV-1 transcripts. To test whether miRNA binding induces virion incorporation, we introduced artificial miRNA target sites into the HIV-1 genome and observed a 10 to 40-fold increase in the packaging of the cognate miRNA into virions, leading to the recruitment of up to 1.6 copies into each virion. Importantly, this high level of incorporation significantly inhibited HIV-1 virion infectivity. We conclude that target sites for cellular miRNAs can inhibit RNA virus replication at two distinct steps, i.e., during infection and during viral gene expression, thus explaining why a range of different RNA viruses appear to have evolved to restrict cellular miRNA binding to their genome.
Project description:To investigate how the major HIV-1 structural protein Gag packages viral genomes efficiently, we replaced the NC domain of Gag with RNA binding domains from heterologous cellular RNA binding proteins to generate Gag chimeras. We hypothesize that the Gag chimeras that preferentially bind to purine-rich RNA sequences will package viral genomes efficiently. We performed CLIP-seq to identify the RNA sequences bound by WT Gag and Gag chimeras in cells, at the plasma membrane, and in virions.
Project description:To investigate how the major HIV-1 structural protein Gag packages viral genomes efficiently, we replaced the NC domain of Gag with RNA binding domains from heterologous cellular RNA binding proteins to generate Gag chimeras. We hypothesize that the Gag chimeras that preferentially bind to purine-rich RNA sequences will package viral genomes efficiently. We performed CLIP-seq to identify the RNA sequences bound by WT Gag and Gag chimeras in cells, at the plasma membrane, and in virions.
Project description:To investigate how the major HIV-1 structural protein Gag packages viral genomes efficiently, we replaced the NC domain of Gag with RNA binding domains from heterologous cellular RNA binding proteins to generate Gag chimeras. We hypothesize that the Gag chimeras that preferentially bind to purine-rich RNA sequences will package viral genomes efficiently. We performed CLIP-seq to identify the RNA sequences bound by WT Gag and Gag chimeras in cells, at the plasma membrane, and in virions.
Project description:HIV-1 incorporates a large array of host proteins into virions. Determining the host protein composition in HIV virions has technical difficulties, including co-purification of microvesicles. We developed an alternative purification technique using cholesterol that differentially modulates the density of virions and microvesicles (density modification, DM) allowing for high-yield virion purification that is essential for tandem mass spectrometric and quantitative proteomic (iTRAQ) analysis. DM purified virions were analyzed using iTRAQ and validated against Optiprep (60% iodixanol) purified virions. We were able to characterize host protein incorporation in DM-purified HIV particles derived from CD4+ T cell lines; we compared this dataset to a reprocessed dataset of monocyte-derived macrophages (MDM) derived HIV-1 searched using PrpArML which uses multiple search algorithms (OMSSA, X!Tandem with native, k-score and s-score scoring, MASCOT, MyriMatch, and InSpecT ). The database used for search was the UniProt-SwissProt database (version 2010.11.02; 522,019 sequences). Peptides were combined on PepARML using a random forest approach (Weka) and the results were then parsed into MASPECTRAS 2 with minimum two peptide for a protein and a spectrum false discovery rate of 5%. Peptides assigned to keratin were excluded, and since the analysis was focused on host proteins, viral peptide assignments were excluded. Protein redundancy was removed by MS based evidence clustering. Link to the paper related to the reprocessed MDM dataset: PMID: 16940516, the dataset itself is not publicly available.
Project description:The objective of this study was to identify the viral transcripts packaged into the virion particles produced from BCBL1 cells as well as virions from 293L cells containing BAC36 BACs RNA from virions were extracted and analyzed by RNA sequencing
Project description:The HIV-1 Gag protein orchestrates all steps of virion genesis, including RNA recruitment into virions. However, the identities of specific RNA sequences recognized by Gag in cells and virions are largely unknown. Using crosslinking-immunoprecipitation (CLIP) sequencing, we uncover dramatic changes in the RNA binding specificity of Gag during virion genesis that are induced by its membrane binding, multimerization and proteolytic maturation. Prior to assembly, and also in mature virions, the nucleocapsid domain of Gag preferentially binds to psi and Rev Response elements in the viral genome, and GU-rich mRNA sequences. However, during assembly of immature virions, this specificity changes in a manner that facilitates genome packaging, as nucleocapsid binds to many sites on the viral genome and mRNA sequences with a similar A-rich nucleotide composition. Additionally, we find that the matrix domain of Gag binds almost exclusively to specific tRNAs in the cytosol, and this association regulates Gag binding to cellular membranes.