HTLV-1 Replication/Reactivation-Induced DNA Damage: Mechanisms and Pathogenesis

HTLV-1 复制/重新激活诱导的 DNA 损伤：机制和发病机制

• 批准号: 10572907
• 负责人: CHOU-ZEN GIAM
• 金额: $ 22.78万
• 依托单位: HENRY M. JACKSON FDN FOR THE ADV MIL/MED
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-11-14 至 2024-10-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10572907
• 关键词: Ablation; Acute; Address; Adult T-Cell Leukemia/Lymphoma; B lymphoid malignancy; Biological; CD4 Positive T Lymphocytes; CRISPR/Cas technology; Cell Cycle; Cell Cycle Arrest; Cell Line; Cell Proliferation; Cells; Characteristics; Chronic; Clonal Expansion; Complex; Copy Number Polymorphism; DNA Damage; DNA Double Strand Break; DNA Sequence; DNA cassette; Data; Development; Evolution; Excision; Feedback; G1/S Transition; Gene Combinations; Genes; Genetic Transcription; Genome; Genomic Instability; Genomics; Human; Human Genome; Human T-lymphotropic virus 1; Hypersensitivity; IRF4 gene; Immune response; Individual; Infection; Latent virus infection phase; Leucine Zippers; Light; Lymphoma cell; Malignant Neoplasms; Maps; Measures; Mediating; Messenger RNA; Mitotic; Molecular; Mutation; NF-kappa B; Oncoproteins; Pathogenesis; Pathway interactions; Persons; Process; Productivity; Proliferating; Proviruses; Recurrence; Regulation; Resistance; Retroviridae; Signal Transduction; Survivors; T-Cell Development; T-Lymphocyte; Taxes; Techniques; Testing; Therapeutic; Time; Trans-Activators; Transcript; Transcription Factor AP-1; Transcription-Coupled Repair; Tumor Suppressor Proteins; Up-Regulation; Variant; Viral; Viral Regulatory Proteins; Virus Diseases; Virus Replication; Xeroderma Pigmentosum; activating transcription factor; c-myc Genes; cell transformation; clastogen; endonuclease; experimental study; gain of function; gain of function mutation; genome-wide; inhibitor; insertion/deletion mutation; nucleic acid structure; prevent; promoter; repair enzyme; response; senescence; synergism; transcription factor; transmission process; ultraviolet irradiation

The human T-cell leukemia virus type 1 (HTLV-1) is a complex human delta retrovirus that infects 10-20 million people worldwide. Approximately 3-5% of infected individuals develop an intractable T cell malignancy known as adult T cell leukemia/lymphoma (ATL) decades later. How HTLV-1 infection progresses to ATL is not fully understood. Two viral regulatory proteins, Tax and HBZ, encoded by the sense and antisense viral mRNA transcripts, respectively, are crucial for causing ATL. Tax, the viral trans-activator/oncoprotein, is a robust activator of viral replication and IKK/NF-κB signaling, and a potent clastogen that induces DNA double-strand breaks (DSBs). It is thought to be the cause for the extensive genomic instability of ATL, which, on average, contains 59.5 structural variations in its genome. We recently discovered that NF-κB hyperactivation by Tax results in the co-transcriptional accumulation of a nucleic acid structure known as an R-loop. And R-loop excision by Xeroderma pigmentosum F (XPF) and XPG, two endonucleases of the transcription-coupled nucleotide excision repair (TC-NER) pathway, leads to DNA DSBs. This finding provides a mechanistic explanation for the genomic instability of ATL and the senescence-inducing activities of Tax. Indeed, NF-κB blockade prevents Tax- induced R-loop accumulation, DNA damage, and senescence. And the silencing of XPF and XPG mitigates Tax senescence, while deficiency in either or both frequently occurs in ATL cells of all types. Importantly, NF-κB is constitutively active in ATL, and ATL cells are resistant to Tax-senescence, suggesting that they have evolved adaptive changes to benefit from the survival and proliferation advantages conferred by Tax and NF-κB. Considering our discoveries outlined above and recent evidence showing that Tax is expressed intermittently in intense bursts in ATL cell lines and HTLV-1-infected T lymphocytes cultured ex vivo, we posit that most de novo HTLV-1 infections result in active viral replication, during which potent NF-κB activation by Tax drives the accumulation of R-loops that promote DNA DSBs, leading to senescence. In a fraction of infected T cells, HTLV- 1 proviruses likely integrate into transcriptionally quiescent chromosomal regions, establishing latent viral infection. During latency, HBZ, expressed from a distinct promoter in the 3’ LTR, dampens Tax activities to inhibit viral replication and, at the same time, stimulates the clonal expansion of the latently infected cells. We further posit that Tax, expressed intermittently during viral reactivation, targets R-loops and DNA DSBs to specific NF- kB-regulated genes, causing their inactivation and facilitating ATL development. Finally, we hypothesize that during ATL evolution, gain-of-function mutations and copy number variants of interferon regulatory factor 4 (IRF4) gene are selected to enable cellular adaptation to the DNA damage and senescence response induced by Tax and NF-κB. We will test these hypotheses in two specific aims: Aim 1 To determine how Tax/NF-κB - induced R-loops impact host cell genome and cell fate. Aim 2 To elucidate how ATL cells accommodate chronic NF-κB activation.

人类T细胞白血病1型（HTLV-1）是一种复杂的人类三角病毒，在全球范围内感染了1000万人。几十年后，大约3-5％的感染个体形成了一种可怕的T细胞恶性肿瘤，称为成年T细胞白血病/淋巴瘤（ATL）。 HTLV-1感染如何发展为ATL。分别由感官和反义病毒mRNA转录本编码的两种病毒调节蛋白，税收和HBZ，对于引起ATL至关重要。税收，病毒反激活剂/癌蛋白是病毒复制和IKK/NF-κB信号传导的鲁棒激活剂，也是诱导DNA双链断裂（DSB）的潜在类基因组。它被认为是ATL广泛基因组不稳定性的原因，平均而言，其基因组中包含59.5个结构变化。我们最近发现，通过税收的NF-κB过度激活导致称为R环的核酸结构的共转录积累。 Xeroderma色素F（XPF）和XPG的R环惊喜，这是转录耦合核苷酸惊喜修复（TC-NER）途径的两个内切酶，导致DNA DSB。这一发现为ATL的基因组不稳定性和税收诱导活动提供了机械解释。实际上，NF-κB桶可以防止税收诱导的R环积累，DNA损伤和感应。 XPF和XPG的沉默会减轻税收的感受，而在所有类型的ATL细胞中，两种缺乏症的缺乏症。重要的是，NF-κB在ATL中一直保持活跃，并且ATL细胞对税收的抗性具有抵抗力，这表明它们已经发展出适应性变化，从而受益于税收和NF-κB的生存和增殖优势。 Considering our discoveries outlined above and recent evidence showing that Tax is expressed intermittently in intense bursts in ATL cell lines and HTLV-1-infected T lymphocytes cultured ex vivo, we positive that most de novo HTLV-1 infections result in active viral replication, during which potential NF-κB activation by Tax drives the accumulation of R-loops that promote DNA DSBs, leading to senscence.在感染的T细胞的一部分中，HTLV-1病毒可能集成到转录的独家染色体区域，从而建立潜在的病毒感染。在延迟期间，HBz从3'LTR中的独特启动子表示，该死的税收活动抑制病毒复制，同时刺激了潜在感染的细胞的克隆扩张。我们进一步肯定的是，在病毒重新激活期间间歇性地表达的税收将R环和DNA DSB靶向特定的NF-KB调节基因，导致其失活并支持ATL的发展。最后，我们假设在ATL演化期间，选择了干扰素调节因子4（IRF4）基因的功能增益突变和拷贝数变异，以使细胞适应DNA损伤和由税收和NF-κB引起的DNA损伤和感应反应。我们将在两个具体目标中检验这些假设：目标1来确定税收/NF-κB如何影响宿主细胞基因组和细胞命运。目标2以阐明ATL细胞如何适应慢性NF-κB激活。