Al Dhaheri Noura Salem, Phillip Pretty Susan, Ghazawi Akela, Ali Jahabar, Beebi Elizabeth, Jaballah Soumeya Ali, Rizvi Tahir A
Department of Microbiology & Immunology, Faculty of Medicine and Health Sciences (FMHS), United Arab Emirates University (UAEU), Al Ain, UAE.
Retrovirology. 2009 Jul 14;6:66. doi: 10.1186/1742-4690-6-66.
The mouse mammary tumor virus (MMTV) is unique from other retroviruses in having multiple viral promoters, which can be regulated by hormones in a tissue specific manner. This unique property has lead to increased interest in studying MMTV replication with the hope of developing MMTV based vectors for human gene therapy. However, it has recently been reported that related as well as unrelated retroviruses can cross-package each other's genome raising safety concerns towards the use of candidate retroviral vectors for human gene therapy. Therefore, using a trans complementation assay, we looked at the ability of MMTV RNA to be cross-packaged and propagated by an unrelated primate Mason-Pfizer monkey virus (MPMV) that has intracellular assembly process similar to that of MMTV.
Our results revealed that MMTV and MPMV RNAs could be cross-packaged by the heterologous virus particles reciprocally suggesting that pseudotyping between two genetically distinct retroviruses can take place at the RNA level. However, the cross-packaged RNAs could not be propagated further indicating a block at post-packaging events in the retroviral life cycle. To further confirm that the specificity of cross-packaging was conferred by the packaging sequences (psi), we cloned the packaging sequences of these viruses on expression plasmids that generated non-viral RNAs. Test of these non-viral RNAs confirmed that the reciprocal cross-packaging was primarily due to the recognition of psi by the heterologous virus proteins.
The results presented in this study strongly argue that MPMV and MMTV are promiscuous in their ability to cross-package each other's genome suggesting potential RNA-protein interactions among divergent retroviral RNAs proposing that these interactions are more complicated than originally thought. Furthermore, these observations raise the possibility that MMTV and MPMV genomes could also co-package providing substrates for exchanging genetic information.
小鼠乳腺肿瘤病毒（MMTV）与其他逆转录病毒不同，它具有多个病毒启动子，这些启动子可通过激素以组织特异性方式进行调控。这种独特的特性使得人们对研究MMTV复制的兴趣增加，希望开发基于MMTV的载体用于人类基因治疗。然而，最近有报道称，相关和不相关的逆转录病毒都可以相互包装彼此的基因组，这引发了对用于人类基因治疗的候选逆转录病毒载体安全性的担忧。因此，我们使用转互补分析方法，研究了MMTV RNA被不相关的灵长类动物梅森 - 辉瑞猴病毒（MPMV）交叉包装和传播的能力，MPMV的细胞内组装过程与MMTV相似。
我们的结果表明，MMTV和MPMV RNA可以被异源病毒颗粒相互交叉包装，这表明两种基因不同的逆转录病毒之间的假型化可以在RNA水平上发生。然而，交叉包装的RNA无法进一步传播，这表明在逆转录病毒生命周期的包装后事件中存在阻滞。为了进一步证实交叉包装的特异性是由包装序列（ψ）赋予的，我们将这些病毒的包装序列克隆到产生非病毒RNA的表达质粒上。对这些非病毒RNA的测试证实，相互交叉包装主要是由于异源病毒蛋白对ψ的识别。
本研究结果有力地表明，MPMV和MMTV在交叉包装彼此基因组的能力上是混杂的，这表明不同逆转录病毒RNA之间可能存在潜在的RNA - 蛋白质相互作用，这表明这些相互作用比最初想象的更为复杂。此外，这些观察结果增加了MMTV和MPMV基因组也可能共同包装从而为交换遗传信息提供底物的可能性。
