Department of Molecular Genetics, Microbiology and Immunology, University of Medicine and Dentistry of New Jersey Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
J Biol Chem. 2010 Jun 25;285(26):19776-84. doi: 10.1074/jbc.M109.085621. Epub 2010 Apr 23.
Programmed -1 ribosomal frameshifting (PRF) is a distinctive mode of gene expression utilized by some viruses, including human immunodeficiency virus type 1 (HIV-1), to produce multiple proteins from a single mRNA. -1 PRF induces a subset of elongating ribosomes to shift their translational reading frame by 1 base in the 5' direction. The appropriate ratio of Gag to Gag-Pol synthesis is tightly regulated by the PRF signal which promotes ribosomes to shift frame, and even small changes in PRF efficiency, either up or down, have significant inhibitory effects upon virus production, making PRF essential for HIV-1 replication. Although little has been reported about the cellular factors that modulate HIV-1 PRF, the cis-acting elements regulating PRF have been extensively investigated, and the PRF signal of HIV-1 was shown to include a slippery site and frameshift stimulatory signal. Recently, a genome-wide screen performed to identify cellular factors that affect HIV-1 replication demonstrated that down-regulation of eukaryotic release factor 1 (eRF1) inhibited HIV-1 replication. Because of the eRF1 role in translation, we hypothesized that eRF1 is important for HIV-1 PRF. Using a dual luciferase reporter system harboring a HIV-1 PRF signal, results showed that depletion or inhibition of eRF1 enhanced PRF in yeast, rabbit reticulocyte lysates, and mammalian cells. Consistent with the eRF1 role in modulating HIV PRF, depleting eRF1 increased the Gag-Pol to Gag ratio in cells infected with replication-competent virus. The increase in PRF was independent of a proximal termination codon and did not result from increased ribosomal pausing at the slippery site. This is the first time that a cellular factor has been identified which can promote HIV-1 PRF and highlights HIV-1 PRF as essential for replication and an important but under exploited antiviral drug target.
-1 核糖体移码（PRF）是一些病毒（包括人类免疫缺陷病毒 1 型，HIV-1）利用的一种独特的基因表达模式，可从单个 mRNA 产生多种蛋白质。-1 PRF 诱导一部分延伸核糖体在 5'方向上移动 1 个碱基的翻译阅读框。PRF 信号对 Gag 和 Gag-Pol 合成的适当比例进行严格调节，该信号促进核糖体移码，甚至 PRF 效率的微小变化（向上或向下）都会对病毒产生显著的抑制作用，使 PRF 成为 HIV-1 复制所必需的。虽然关于调节 HIV-1 PRF 的细胞因子的报道很少，但已经广泛研究了调节 PRF 的顺式作用元件，并且 HIV-1 的 PRF 信号被证明包括滑码位点和移码刺激信号。最近，进行了一项全基因组筛选以鉴定影响 HIV-1 复制的细胞因子，结果表明下调真核释放因子 1（eRF1）可抑制 HIV-1 复制。由于 eRF1 在翻译中的作用，我们假设 eRF1 对 HIV-1 PRF 很重要。使用含有 HIV-1 PRF 信号的双荧光素酶报告系统，结果表明在酵母、兔网织红细胞裂解物和哺乳动物细胞中，eRF1 的耗尽或抑制增强了 PRF。与 eRF1 调节 HIV PRF 的作用一致，耗尽 eRF1 增加了感染复制能力病毒的细胞中的 Gag-Pol 与 Gag 的比值。PRF 的增加与近端终止密码子无关，也不会导致滑码位点处核糖体暂停增加。这是首次鉴定出可促进 HIV-1 PRF 的细胞因子，并强调了 HIV-1 PRF 对复制的重要性，以及作为重要但未充分利用的抗病毒药物靶标。
