Laboratory of Viral and Cellular Genetics, Institute of Molecular Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic.
Laboratory of Anaerobic Microbiology, Institute of Animal Physiology and Genetics of the Czech Academy of Sciences, Vídeňská 1083, 142 20 Prague 4, Czech Republic.
Viruses. 2024 Sep 25;16(10):1518. doi: 10.3390/v16101518.
Retroviruses integrate into the genomes of infected host cells to form proviruses, a genetic platform for stable viral gene expression. Epigenetic silencing can, however, hamper proviral transcriptional activity. As gammaretroviruses (γRVs) preferentially integrate into active promoter and enhancer sites, the high transcriptional activity of γRVs can be attributed to this integration preference. In addition, long terminal repeats (LTRs) of some γRVs were shown to act as potent promoters by themselves. Here, we investigate the capacity of different γRV LTRs to drive stable expression within a non-preferred epigenomic environment in the context of diverse retroviral vectors. We demonstrate that different γRV LTRs are either rapidly silenced or remain active for long periods of time with a predominantly active proviral population under normal and retargeted integration. As an alternative to the established γRV systems, the feline leukemia virus and koala retrovirus LTRs are able to drive stable, albeit intensity-diverse, transgene expression. Overall, we show that despite the occurrence of rapid silencing events, most γRV LTRs can drive stable expression outside of their preferred chromatin landscape after retrovirus integrations.
逆转录病毒将自身整合到受感染宿主细胞的基因组中，形成前病毒，这是病毒基因稳定表达的遗传平台。然而，表观遗传沉默可能会阻碍前病毒的转录活性。由于γ 逆转录病毒（γRV）优先整合到活跃的启动子和增强子位点，因此 γRV 的高转录活性可归因于这种整合偏好。此外，一些 γRV 的长末端重复序列（LTR）本身就被证明具有很强的启动子活性。在这里，我们研究了不同的 γRV LTR 在不同逆转录病毒载体的非优先表观基因组环境中驱动稳定表达的能力。我们证明，不同的 γRV LTR 要么迅速沉默，要么在正常和重定向整合的情况下，主要是活跃的前病毒群体，保持长时间的活跃。作为已建立的 γRV 系统的替代方案，猫白血病病毒和树袋熊逆转录病毒 LTR 能够驱动稳定的，尽管强度不同的转基因表达。总的来说，我们表明，尽管存在快速沉默事件，但大多数 γRV LTR 在前病毒整合后，可以在其偏好的染色质景观之外驱动稳定表达。
