Correct capsid assembly mediated by a conserved YXXLGL motif in prototype foamy virus Gag is essential for infectivity and reverse transcription of the viral genome
Correct capsid assembly mediated by a conserved YXXLGL motif in prototype foamy virus Gag is essential for infectivity and reverse transcription of the viral genome
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DOI：
10.1128/jvi.01866-06
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发表时间：
2007-04-01
影响因子：
5.4
通讯作者：
Lindemann, Dirk
中科院分区：
文献类型：
--
作者：
Mannigel, Ingrid;Stange, Annett;Lindemann, Dirk
与其他逆转录病毒 Gag 蛋白不同，原型泡沫病毒 (PFV) p71(gag) 蛋白不会加工成成熟基质 (NU)、衣壳 (CA) 和核衣壳 (NC) 亚基。关于 FV 衣壳组装和释放所涉及的序列基序的信息很少。最近对 PFV Gag 中候选 L 结构域基序的分析发现了一个进化上保守的 YXXL 序列基序，在衣壳组装中具有潜在功能。在这里，我们通过证明与 PFV Gag PSAP L 结构域基序不同，它不能在功能上被异源 L 结构域序列替代，为这一假设提供了支持，即该基序的功能不像传统的 L 结构域。此外，单个氨基酸 Y-464、I-466、L-467 和 L-469（而非 E-465）突变为丙氨酸，导致颗粒释放减少和非感染性异常衣壳结构的产生，尽管相对结构蛋白的掺入和加工并未受到影响。相比之下，G(468) 突变为丙氨酸会产生中间的、温度敏感的表型，其特征是颗粒释放减少和感染性降低。尽管所有突变体的相对RNA基因组掺入相似，但对颗粒相关病毒核酸的分析和定量表明，所有非感染性突变体的基因组逆转录存在缺陷，与正逆转录病毒不同，就FV而言，这一过程发生在病毒产生细胞中。与感染性降低相关，G(468)A 突变体表现出中等水平的基因组逆转录。综上所述，这些结果表明 PFV Gag 中保守的 YXXLGL 基序参与正确的衣壳组装，这反过来对于 FV 基因组的逆转录至关重要。
Unlike other retrovirus Gag proteins, the prototype foamy virus (PFV) p71(gag) protein is not processed into mature matrix (NU), capsid (CA), and nucleocapsid (NC) subunits. Little information about sequence motifs involved in FV capsid assembly and release is available. The recent analysis of candidate L-domain motifs in PFV Gag identified an evolutionarily conserved YXXL sequence motif with a potential function in capsid assembly. Here we provide support for the hypothesis that this motif does not function like a conventional L domain, by demonstrating that, unlike the PFV Gag PSAP L-domain motif, it cannot be functionally replaced by heterologous L-domain sequences. Furthermore, mutation of individual amino acids Y-464, I-466, L-467, and L-469, but not E-465, to alanine led to reduced particle release and production of noninfectious, aberrant capsid structures, although relative structural protein incorporation and processing were not affected. In contrast, mutation of G(468) to alanine resulted in an intermediate, temperature-sensitive phenotype characterized by reduced particle release and reduced infectivity. Despite similar relative RNA genome incorporation for all mutants, analysis and quantification of particle-associated viral nucleic acids demonstrated defects in genomic reverse transcription for all the noninfectious mutants, a process that, unlike that of orthoretroviruses, in the case of FVs takes place in the virus-producing cell. In correlation with the reduced infectivity, the G(468)A mutant displayed an intermediate level of genomic reverse transcription. Taken together, these results demonstrate that the conserved YXXLGL motif in PFV Gag is involved in correct capsid assembly, which in turn is essential for reverse transcription of the FV genome.