Department of Biology, College of Arts and Sciences, Howard Universitygrid.257127.4, Washington, D.C., USA.
Section on Immune Biology of Retroviral Infection, Vaccine Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
Microbiol Spectr. 2022 Feb 23;10(1):e0188121. doi: 10.1128/spectrum.01881-21. Epub 2022 Jan 12.
Cells increase their DNA content greater than the G2/M (DNA > 4n) phases along the path to cancer. The signals that support this increase in DNA content remain poorly understood. Cells infected with adenovirus (Ad) similarly develop DNA > 4n and share a need to bypass the DNA damage response (DDR) signals that trigger cell cycle arrest, and/or cell death. Ads with deletion in early region 1B55K (Δ Ad) are oncolytic agents that are currently being explored for use in vaccine delivery. Interestingly, they promote higher levels of DNA > 4n than Ads that contain E1B55K. Existing in these and almost all Ads that are being explored for clinical use, is early region 4 (E4). The Ad E4 open reading frame 3 (E4orf3) is a viral oncogene that interferes with the ability of cells to respond to DNA damage by disrupting MRN complex formation. Our study reveals that E4orf3 is required for the enhanced fraction of Δ Ad-infected cells with DNA > 4n. For that reason, we explored signaling events mediated by E4orf3. We found that in Δ Ad-infected cells, E4orf3, as reported by others, isolates NBS1 in nuclear dots and tracks. This allows for elevated levels of phosphorylated ATM that is linked to transcriptionally active NF-κB. Pharmacological inhibition of NF-κB reduced the fraction of Δ Ad-infected cells with DNA > 4n while pharmacological inhibition of ATM reduced the levels of nuclear NF-κB and the fraction of Δ Ad-infected cells with DNA > 4n and increased the fraction of dead or dying cells with fragmented DNA. This ability of E4orf3 to disrupt MRN complex formation that allows cells to bypass the cell cycle, evade death, and accumulate DNA > 4n, may be linked to its oncogenic potential. Genome instability, a hallmark of cancer, exists as part of a cycle that leads to DNA damage and DNA > 4n that further enhances genome instability. Ad E4orf3 is a viral oncogene. Here, we describe E4orf3 mediated signaling events that support DNA > 4n in Δ Ad-infected cells. These signaling events may be linked to the oncogenic potential of E4orf3 and may provide a basis for how some cells survive with DNA > 4n.
细胞在向癌症发展的过程中，其 DNA 含量会增加到 G2/M（DNA>4n）阶段以上。支持这种 DNA 含量增加的信号仍然知之甚少。感染腺病毒（Ad）的细胞也会出现 DNA>4n，并需要绕过触发细胞周期停滞和/或细胞死亡的 DNA 损伤反应（DDR）信号。早期区域 1B55K 缺失的 Ad（ΔAd）是溶瘤病毒，目前正在探索用于疫苗传递。有趣的是，它们促进的 DNA>4n 水平高于包含 E1B55K 的 Ad。在这些 Ad 中以及几乎所有正在探索用于临床应用的 Ad 中，都存在早期区域 4（E4）。腺病毒 E4 开放阅读框 3（E4orf3）是一种病毒癌基因，通过破坏 MRN 复合物的形成，干扰细胞对 DNA 损伤做出反应的能力。我们的研究表明，E4orf3 是ΔAd 感染细胞中具有 DNA>4n 的增强部分所必需的。因此，我们探索了由 E4orf3 介导的信号事件。我们发现，在ΔAd 感染的细胞中，E4orf3 正如其他人所报道的那样，将 NBS1 隔离在核点和轨道中。这使得磷酸化 ATM 的水平升高，与转录活性 NF-κB 相关联。NF-κB 的药理学抑制减少了具有 DNA>4n 的ΔAd 感染细胞的比例，而 ATM 的药理学抑制降低了核 NF-κB 的水平和具有 DNA>4n 的ΔAd 感染细胞的比例，并增加了具有碎片化 DNA 的死亡或垂死细胞的比例。E4orf3 破坏 MRN 复合物的形成能力，使细胞能够绕过细胞周期、逃避死亡并积累 DNA>4n，这可能与其致癌潜力有关。基因组不稳定性是癌症的一个标志，它是导致 DNA 损伤和 DNA>4n 的循环的一部分，进一步增强了基因组不稳定性。腺病毒 E4orf3 是一种病毒癌基因。在这里，我们描述了 E4orf3 介导的信号事件，这些信号事件支持ΔAd 感染细胞中的 DNA>4n。这些信号事件可能与 E4orf3 的致癌潜力有关，并为一些细胞如何在具有 DNA>4n 的情况下存活提供了依据。
