Summers Monnette F, Haubold MegAnn K, Morgenstern Marcel, Shepherd Phoenix, Larsen Clairine I S, Bartz Ava E, Thirumoorthy Gopishankar, Kirchdoerfer Robert N, Coon Joshua J, Mehta Kavi P M, Majumder Kinjal
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
McArdle Laboratory for Cancer Research, School of Medicine and Public health, Madison, Wisconsin, United States of America.
PLoS Pathog. 2025 Aug 18;21(8):e1013142. doi: 10.1371/journal.ppat.1013142. eCollection 2025 Aug.
Parvoviruses are single-stranded DNA viruses that have been modified to serve as vehicles for therapeutic transgene delivery in the form of recombinant Adeno-Associated Virus (rAAV2) vectors or rodent parvovirus-derived oncolytic agents. Infection with viruses of the Parvoviridae family induces a cellular DNA Damage Response (DDR) signal that supports virus replication. However, it remains unknown whether rAAV2 vectors or non-replicative wild-type AAV2 (wtAAV2) genomes induce cellular DDR signals, which might be deleterious to the cell. To determine the impact of wtAAV2/rAAV2 genomes on the integrity of the host chromosome, we have pulsed wtAAV2/rAAV2 infected cells with BrdU analogs followed by single-molecule imaging of the cellular replisomes and proteomic analysis of the host replication forks. We discovered that non-replicative wtAAV2/rAAV2 genomes are sufficient to induce replication stress on the host genome, leading to DDR signals in a dose-dependent manner. Moreover, infection with replication-competent wtAAV2 leads to enrichment of replication stress proteins, DNA repair factors and RNA processing machinery on cellular replication forks. However, neither the wtAAV2 Inverted Terminal Repeats (ITRs) that are retained in rAAV2s nor empty capsids are sufficient to induce host-cell replication stress. Strikingly, incoming wtAAV2 genomes associate with the single-stranded DNA binding protein RPA in host cells in a dose-dependent manner, progressively shortening cellular replication forks. These elevated levels of wtAAV2-induced cellular replication stress eventually leads to accumulation of DDR signals in the nucleus. Chemical inhibition of RPA activity and RNAi-mediated knockdown leads to de-repression of the wtAAV2 genome, increasing Rep 68/78 gene expression. Ectopic expression of RPA rescues wtAAV2-induced replication stress. Taken together, our findings suggest that depletion of cellular stores of RPA molecules by competing wtAAV2 genomes restrict viral gene expression and cause cellular DNA damage.
细小病毒是单链DNA病毒,已被改造为以重组腺相关病毒(rAAV2)载体或啮齿动物细小病毒衍生的溶瘤剂形式用于治疗性转基因递送的载体。感染细小病毒科病毒会诱导一种支持病毒复制的细胞DNA损伤反应(DDR)信号。然而,rAAV2载体或非复制性野生型AAV2(wtAAV2)基因组是否会诱导细胞DDR信号仍不清楚,而这种信号可能对细胞有害。为了确定wtAAV2/rAAV2基因组对宿主染色体完整性的影响,我们用BrdU类似物脉冲感染wtAAV2/rAAV2的细胞,随后对细胞复制体进行单分子成像,并对宿主复制叉进行蛋白质组分析。我们发现,非复制性wtAAV2/rAAV2基因组足以在宿主基因组上诱导复制应激,以剂量依赖的方式导致DDR信号。此外,感染具有复制能力的wtAAV2会导致细胞复制叉上复制应激蛋白、DNA修复因子和RNA加工机制的富集。然而,rAAV2中保留的wtAAV2反向末端重复序列(ITRs)或空衣壳都不足以诱导宿主细胞复制应激。令人惊讶的是,进入的wtAAV2基因组以剂量依赖的方式与宿主细胞中的单链DNA结合蛋白RPA结合,逐渐缩短细胞复制叉。这些wtAAV2诱导的细胞复制应激水平升高最终导致细胞核中DDR信号的积累。对RPA活性的化学抑制和RNAi介导的敲低导致wtAAV2基因组的去抑制,增加Rep 68/78基因的表达。RPA的异位表达挽救了wtAAV2诱导的复制应激。综上所述,我们的研究结果表明,竞争性wtAAV2基因组耗尽细胞内RPA分子储备会限制病毒基因表达并导致细胞DNA损伤。