Background A protein exhibiting more than one biochemical function is termed a moonlighting protein. Glycolytic enzymes are typical moonlighting proteins, and these enzymes control the infection of various viruses. Previously, we reported that glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and alpha-enolase (ENO1) are incorporated into human immunodeficiency virus type 1 (HIV-1) particles from viral producer cells and suppress viral reverse transcription independently each other. However, it remains unclear whether these proteins expressed in viral target cells affect the early phase of HIV-1 replication. Results Here we show that the GAPDH expression level in viral target cells does not affect the early phase of HIV-1 replication, but ENO1 has a capacity to suppress viral integration in viral target cells. In contrast to GAPDH, suppression of ENO1 expression by RNA interference in the target cells increased viral infectivity, but had no effect on the expression levels of the HIV-1 receptors CD4, CCR5 and CXCR4 and on the level of HIV-1 entry. Quantitative analysis of HIV-1 reverse transcription products showed that the number of copies of the late products (R/ gag ) and two-long-terminal-repeat circular forms of viral cDNAs did not change but that of the integrated (Alu- gag ) form increased. In contrast, overexpression of ENO1 in viral target cells decreased viral infectivity owing to the low viral integration efficiency. Results of subcellular fractionation experiments suggest that the HIV integration at the nucleus was negatively regulated by ENO1 localized in the nucleus. In addition, the overexpression of ENO1 in both viral producer cells and target cells most markedly suppressed the viral replication. Conclusions These results indicate that ENO1 in the viral target cells prevents HIV-1 integration. Importantly, ENO1, but not GAPDH, has the bifunctional inhibitory activity against HIV-1 replication. The results provide and new insights into the function of ENO1 as a moonlighting protein in HIV-1 infection.

中文翻译：

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病毒靶细胞中的α-烯醇酶抑制人类免疫缺陷病毒1型整合

背景 表现出一种以上生化功能的蛋白质被称为月光蛋白。糖酵解酶是典型的兼职蛋白，这些酶控制着各种病毒的感染。以前，我们报道了甘油醛 3-磷酸脱氢酶 (GAPDH) 和 α-烯醇化酶 (ENO1) 被纳入来自病毒生产细胞的人类免疫缺陷病毒 1 型 (HIV-1) 颗粒中，并相互独立地抑制病毒逆转录。然而，尚不清楚这些在病毒靶细胞中表达的蛋白质是否会影响 HIV-1 复制的早期阶段。结果 在这里，我们表明病毒靶细胞中的 GAPDH 表达水平不影响 HIV-1 复制的早期阶段，但 ENO1 具有抑制病毒靶细胞中病毒整合的能力。与 GAPDH 相比，通过靶细胞中的 RNA 干扰抑制 ENO1 表达增加了病毒感染性，但对 HIV-1 受体 CD4、CCR5 和 CXCR4 的表达水平以及 HIV-1 进入水平没有影响。HIV-1逆转录产物的定量分析表明，病毒cDNA的晚期产物（R/gag）和两个长末端重复环状形式的拷贝数没有变化，但整合的（Alu-gag）拷贝数没有变化。形式增加。相比之下，由于病毒整合效率低，ENO1 在病毒靶细胞中的过表达降低了病毒的感染性。亚细胞分离实验的结果表明，细胞核中的 HIV 整合受到位于细胞核中的 ENO1 的负调控。此外，ENO1 在病毒生产细胞和靶细胞中的过表达最显着地抑制了病毒复制。结论 这些结果表明病毒靶细胞中的 ENO1 阻止 HIV-1 整合。重要的是，ENO1 而非 GAPDH 具有针对 HIV-1 复制的双功能抑制活性。结果提供了对 ENO1 作为 HIV-1 感染中的临时蛋白的功能的新见解。