Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany.
Institute for Molecular Infection Biology, Julius-Maximilians-Universität Wϋrzburg, Josef-Schneider-Straße 2, 97080 Wϋrzburg, Germany.
Viruses. 2018 Nov 21;10(11):656. doi: 10.3390/v10110656.
Human herpesvirus-6A and -6B (HHV-6A and -6B) are two closely related betaherpesviruses that infect humans. Upon primary infection they establish a life-long infection termed latency, where the virus genome is integrated into the telomeres of latently infected cells. Intriguingly, HHV-6A/B can integrate into germ cells, leading to individuals with inherited chromosomally-integrated HHV-6 (iciHHV-6), who have the HHV-6 genome in every cell. It is known that telomeric repeats flanking the virus genome are essential for integration; however, the protein factors mediating integration remain enigmatic. We have previously shown that the putative viral integrase U94 is not essential for telomere integration; thus, we set out to assess the contribution of potential viral recombination proteins U41 and U70 towards integration. We could show that U70 enhances dsDNA break repair via a homology-directed mechanism using a reporter cell line. We then engineered cells to produce shRNAs targeting both U41 and U70 to inhibit their expression during infection. Using these cells in our HHV-6A in vitro integration assay, we could show that U41/U70 were dispensable for telomere integration. Furthermore, additional inhibition of the cellular recombinase Rad51 suggested that it was also not essential, indicating that other cellular and/or viral factors must mediate telomere integration.
人类疱疹病毒 6A 和 -6B（HHV-6A 和 -6B）是两种密切相关的β疱疹病毒，可感染人类。初次感染后，它们会建立一种称为潜伏期的终身感染，病毒基因组整合到潜伏感染细胞的端粒中。有趣的是，HHV-6A/B 可以整合到生殖细胞中，导致个体遗传染色体整合 HHV-6（iciHHV-6），每个细胞都有 HHV-6 基因组。已知病毒基因组侧翼的端粒重复序列对于整合至关重要；然而，介导整合的蛋白因子仍然是个谜。我们之前已经表明，假定的病毒整合酶 U94对于端粒整合不是必需的；因此，我们着手评估潜在的病毒重组蛋白 U41 和 U70 对整合的贡献。我们可以证明 U70 通过同源定向机制增强 dsDNA 断裂修复，使用报告细胞系。然后，我们设计了产生针对 U41 和 U70 的 shRNA 的细胞，以在感染期间抑制它们的表达。在我们的 HHV-6A 体外整合测定中使用这些细胞，我们可以证明 U41/U70 对于端粒整合不是必需的。此外，细胞重组酶 Rad51 的额外抑制表明它也不是必需的，这表明其他细胞和/或病毒因子必须介导端粒整合。
