Institut National de la Santé et de la Recherche Médicale (INSERM) U941, Paris, France.
PLoS One. 2013;8(1):e52434. doi: 10.1371/journal.pone.0052434. Epub 2013 Jan 8.
Because uncoating of the capsid is linked to reverse transcription, modifications that delay this process lead to the persistence in the cytoplasm of capsids susceptible to recognition by the human restriction factor TRIM5α (hTRIM5α). It is unknown, however, if increasing the time available for capsid-hTRIM5α interactions would actually render viruses more sensitive to hTRIM5α.
Viral sensitivity to hTRIM5α was evaluated by comparing their replication in human U373-X4 cells in which hTRIM5α activity had or had not been inhibited by overexpression of human TRIM5γ. No differences were observed comparing wild-type HIV-1 and variants carrying mutations in reverse transcriptase or the central polypurine tract that delayed the completion of reverse transcription. In addition, the effect of delaying the onset of reverse transcription for several hours by treating target cells with nevirapine was evaluated using viral isolates with different sensitivities to hTRIM5α. Delaying reverse transcription led to a time-dependent loss in viral infectivity that was increased by inhibiting capsid-cyclophilin A interactions, but did not result in increased viral sensitivity to hTRIM5α, regardless of their intrinsic sensitivity to this restriction factor.
Consistent with prior studies, the HIV-1 capsid can be targeted for destruction by hTRIM5α, but different strains display considerable variability in their sensitivity to this restriction factor. Capsids can also be lost more slowly through a TRIM5α-independent process that is accelerated when capsid-cyclophilin A interactions are inhibited, an effect that may reflect changes in the intrinsic stability of the capsid. Blocking the onset or delaying reverse transcription does not, however, increase viral sensitivity to hTRIM5α, indicating that the recognition of the capsids by hTRIM5α is completed rapidly following entry into the cytoplasm, as previously observed for the simian restriction factors TRIM-Cyp and rhesus TRIM5α.
由于衣壳脱壳与逆转录相关联，因此，延迟该过程的修饰会导致衣壳在细胞质中持续存在，从而易于被人类限制因子 TRIM5α（hTRIM5α）识别。但是，增加衣壳与 hTRIM5α 相互作用的时间是否会使病毒对 hTRIM5α 更敏感，目前尚不清楚。
通过比较 hTRIM5α 活性是否被人源 TRIM5γ 过表达抑制来评估病毒对 hTRIM5α 的敏感性，从而评估病毒对 hTRIM5α 的敏感性。比较野生型 HIV-1 与携带逆转录酶或中央多嘧啶区突变的变体时，未观察到差异，这些突变会延迟逆转录的完成。此外，通过用奈韦拉平处理靶细胞来延迟逆转录的起始数小时，评估了具有不同 hTRIM5α 敏感性的病毒分离物。延迟逆转录会导致病毒感染力随时间的推移而逐渐丧失，而抑制衣壳-亲环素 A 相互作用会增加这种丧失，但不会导致病毒对 hTRIM5α 的敏感性增加，而不管它们对这种限制因子的固有敏感性如何。
与先前的研究一致，HIV-1 衣壳可以被 hTRIM5α 靶向破坏，但不同株系对这种限制因子的敏感性存在很大差异。衣壳也可以通过一种独立于 TRIM5α 的过程缓慢丢失，当抑制衣壳-亲环素 A 相互作用时，该过程会加速，这种作用可能反映了衣壳的固有稳定性发生变化。但是，阻止逆转录的起始或延迟不会增加病毒对 hTRIM5α 的敏感性，这表明 hTRIM5α 对衣壳的识别在细胞质中进入后迅速完成，如先前观察到的猴源限制因子 TRIM-Cyp 和恒河猴 TRIM5α 一样。
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