Department of Molecular and Medical Pharmacology, Molecular Biology Institute and UCLA AIDS Institute, UCLA School of Medicine, Los Angeles, California 90095, USA.
J Virol. 2010 May;84(10):5181-90. doi: 10.1128/JVI.02382-09. Epub 2010 Mar 10.
After membrane fusion with a target cell, the core of human immunodeficiency virus type 1 (HIV-1) enters into the cytoplasm, where uncoating occurs. The cone-shaped core is composed of the viral capsid protein (CA), which disassembles during uncoating. The underlying factors and mechanisms governing uncoating are poorly understood. Several CA mutations can cause changes in core stability and a block at reverse transcription, demonstrating the requirement for optimal core stability during viral replication. HIV-1 integrase (IN) catalyzes the insertion of the viral cDNA into the host genome, and certain IN mutations are pleiotropic. Similar to some CA mutants, two IN mutants, one with a complete deletion of IN (NL-DeltaIN) and the other with a Cys-to-Ser substitution (NL-C130S), were noninfectious, with a replication block at reverse transcription. Compared to the wild type (WT), the cytoplasmic CA levels of the IN mutants in infected cells were reduced, suggesting accelerated uncoating. The role of IN during uncoating was examined by isolating and characterizing cores from NL-DeltaIN and NL-C130S. Both IN mutants could form functional cores, but the core yield and stability were decreased. Also, virion incorporation of cyclophilin A (CypA), a cellular peptidyl-prolyl isomerase that binds specifically to CA, was decreased in the IN mutants. Cores isolated from WT virus depleted of CypA had an unstable-core phenotype, confirming a role of CypA in promoting optimal core stability. Taken together, our results indicate that IN is required during uncoating for maintaining CypA-CA interaction, which promotes optimal stability of the viral core.
病毒膜与靶细胞融合后，人类免疫缺陷病毒 1 型（HIV-1）的核心进入细胞质，在细胞质中发生脱壳。锥形核心由病毒衣壳蛋白（CA）组成，在脱壳过程中会解体。脱壳的潜在因素和机制尚不清楚。一些 CA 突变可导致核心稳定性发生变化，并阻断逆转录，这表明在病毒复制过程中需要最佳的核心稳定性。HIV-1 整合酶（IN）催化病毒 cDNA 插入宿主基因组，某些 IN 突变具有多效性。类似于一些 CA 突变体，两种 IN 突变体，一种是 IN 完全缺失（NL-DeltaIN），另一种是 Cys 到 Ser 取代（NL-C130S），均无感染性，逆转录复制受阻。与野生型（WT）相比，感染细胞中 IN 突变体的细胞质 CA 水平降低，提示脱壳加速。通过从 NL-DeltaIN 和 NL-C130S 中分离和鉴定核心来研究 IN 在脱壳过程中的作用。两个 IN 突变体都可以形成功能性核心，但核心产量和稳定性降低。此外，细胞肽基脯氨酰顺反异构酶 cyclophilin A（CypA）与 CA 特异性结合，其在 IN 突变体中的病毒粒子掺入减少。从 WT 病毒中去除 CypA 后分离出的核心表现出不稳定核心表型，证实了 CypA 在促进最佳核心稳定性方面的作用。总之，我们的结果表明，在脱壳过程中需要 IN 来维持 CypA-CA 相互作用，从而促进病毒核心的最佳稳定性。
