Clever J L, Taplitz R A, Lochrie M A, Polisky B, Parslow T G
Departments of Pathology, University of California, San Francisco, California 94143-0506, USA.
J Virol. 2000 Jan;74(1):541-6. doi: 10.1128/jvi.74.1.541-546.2000.
Retroviral RNA encapsidation depends on the specific binding of Gag proteins to packaging (psi) signals in genomic RNA. We investigated whether an in vitro-selected, high-affinity RNA ligand for the nucleocapsid (NC) portion of the Gag protein from human immunodeficiency virus type 1 (HIV-1) could mediate packaging into HIV-1 virions. We find that this ligand can functionally substitute for one of the Gag-binding elements (termed SL3) in the HIV-1 psi locus to support packaging and viral infectivity in cis. By contrast, this ligand, which fails to dimerize spontaneously in vitro, is unable to replace a different psi element (termed SL1) which is required for both Gag binding and dimerization of the HIV-1 genome. A single point mutation within the ligand that eliminates high-affinity in vitro Gag binding also abolishes its packaging activity at the SL3 position. These results demonstrate that specific binding of Gag or NC protein is a critical determinant of genomic RNA packaging.
逆转录病毒RNA的包装依赖于Gag蛋白与基因组RNA中包装（ψ）信号的特异性结合。我们研究了一种体外筛选的、与人免疫缺陷病毒1型（HIV-1）Gag蛋白的核衣壳（NC）部分具有高亲和力的RNA配体是否能够介导其包装进入HIV-1病毒颗粒。我们发现，该配体能够在功能上替代HIV-1 ψ基因座中的一个Gag结合元件（称为SL3），以支持顺式包装和病毒感染性。相比之下，这种在体外不能自发二聚化的配体，无法替代HIV-1基因组Gag结合和二聚化所需的另一个ψ元件（称为SL1）。配体内一个消除体外Gag高亲和力结合的单点突变，也会消除其在SL3位置的包装活性。这些结果表明，Gag或NC蛋白的特异性结合是基因组RNA包装的关键决定因素。
