title: Splicing affects presentation of RNA dimerization signals in HIV-2 in vitro.
abstract: During retroviral replication, full-length viral RNAs are encapsidated into new virus particles, while spliced RNAs are excluded. The Retroviridae are unique among viruses in that infectious viral particles contain a dimer of two identical genomic RNA strands. A variety of experimental data has suggested that dimerization and encapsidation of full-length viral RNAs are linked processes, although whether dimerization is a prerequisite for encapsidation, or conversely, dimerization follows encapsidation, has not been firmly established. If dimerization was the sole determinant for encapsidation, then spliced viral RNAs might be expected to display a reduced capacity for dimerization, resulting in their exclusion from the dimerization pool. Here, we studied the in vitro dimerization properties of unspliced and spliced HIV-2 RNA. We find that the rate and yield of dimerization of Nef, Rev and Tat spliced RNAs exceeded those of unspliced RNA. Although these data do not support a simple correlation between dimerization efficiency and the presence of introns, they establish that splicing affects the presentation of dimerization signal(s), which we corroborate with structure probing. This change in RNA conformation likely affects the RNA's suitability for packaging. Furthermore, the presence of upstream and downstream elements that affect the conformation of the packaging signal represents a potentially efficient viral strategy for correctly sorting spliced versus unspliced RNAs.
authors.affiliation: Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Lanchy
authors.forename: Quenna N
authors.initials: QN
authors.lastname: Szafran
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Lodmell
mesh_terms: D001483:Base Sequence; D019281:Dimerization; D015693:Gene Products, nef / Q000235:genetics / Q000378:metabolism; D015694:Gene Products, rev / Q000235:genetics / Q000378:metabolism; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D016325:HIV Long Terminal Repeat; D015498:HIV-2 / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry / Q000378:metabolism*; D038621:Regulatory Sequences, Ribonucleic Acid; D015398:Signal Transduction; D054311:nef Gene Products, Human Immunodeficiency Virus; D054321:rev Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015693:Gene Products, nef; D015694:Gene Products, rev; D015696:Gene Products, tat; D012333:RNA, Messenger; D012367:RNA, Viral; D038621:Regulatory Sequences, Ribonucleic Acid; D054311:nef Gene Products, Human Immunodeficiency Virus; D054321:rev Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus