Assembly, part of the late stages of the retroviral life cycle, begins when the structural polyprotein Gag associates with viral genomic RNA. Ultimately, more than a thousand Gag molecules form a spherical immature virion. Maturation takes place soon after or concomitantly with virus budding and is initiated as Gag is cleaved by the retroviral protease into its constituent protein domains. The immature core is thought to disassemble and the liberated CA proteins to reassemble into a morphologically distinct mature capsid. In vitro assembly with derivatives of Gag and CA has been used to study retroviruses for over two decades. In this review, we examine the discovery and development of three major model systems [human immunodeficiency virus type 1 (HIV-1), Rous sarcoma virus (RSV), and Mason-Pfizer monkey virus (MPMV)] and discuss structural features and aspects of the retroviral assembly pathway that have been uncovered using in vitro assembly. We also put forward two major unresolved questions in the field and propose future avenues of research.

中文翻译：

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逆转录病毒的体外组装。

组装是逆转录病毒生命周期后期阶段的一部分，当结构多蛋白Gag与病毒基因组RNA结合时开始组装。最终，超过一千个Gag分子形成了球形的未成熟病毒体。成熟期发生在病毒出芽后不久或与之同时发生，并且随着Gag被逆转录病毒蛋白酶切割成其组成蛋白域而开始。不成熟的核心被认为会分解，而释放的CA蛋白会重新组装成形态上截然不同的成熟衣壳。与Gag和CA的衍生物进行体外组装已用于研究逆转录病毒已有二十多年了。在这篇综述中，我们研究了三种主要模型系统的发现和开发[人类免疫缺陷病毒1型（HIV-1），劳斯肉瘤病毒（RSV），和Mason-Pfizer猴病毒（MPMV）]，并讨论了使用体外组装发现的逆转录病毒组装途径的结构特征和方面。我们还提出了该领域中两个尚未解决的主要问题，并提出了未来的研究途径。