MOUSE MAMMARY TUMOR VIRUS AND DETERMINANTS OF LEUKEMOGENICITY

小鼠乳腺肿瘤病毒（MMTV）主要在小鼠中诱导乳腺癌。然而，一些高度相关的MMTV毒株（例如，TBLV）诱导T细胞肿瘤，但不诱导乳腺癌。前病毒DNA末端（LTR）之间的主要差异。这些差异包括（i）在淋巴组织（包括胸腺）中抑制MMTV转录的负调控元件（NRE）的缺失，（ii）参与MMTV从淋巴细胞向乳腺细胞传播的超抗原基因C-末端三分之一的缺失，以及（iii）LTR缺失侧翼62 bp的三倍。在这项拨款申请中，将评估负责胸腺向性的TBLV基因组区域。首先，将分析TBLV感染的特定细胞类型，并确定最佳感染途径。第二，将已知NRE中的特定突变，sag开放阅读框的三重区引入亲乳腺MMTV中，并测试它们感染特定细胞类型和引起白血病的能力。第三，将分析显示增强MMTV在T细胞中转录的三重区与细胞转录因子的结合，并鉴定这些因子。第四，如果LTR不足以复制TBLV的细胞类型嗜性和致白血病性，我们将构建MMTV的亲乳腺和亲胸腺株之间的嵌合体，并测试这些嵌合体感染不同细胞类型和诱导疾病的能力。在第二个具体目标中，我们将继续我们的研究，以评估特定TBLV整合位点在病毒诱导的白血病中的作用。将通过PCR和脉冲场凝胶电泳分析先前鉴定的TBLV整合。还将在由MMTV前病毒诱导的白血病中评估c-myc基因座中的整合，所述MMTV前病毒具有截短的sag基因并且缺乏NRE，但也缺乏TBLV中发现的特异性三重区。这些实验和研究的转基因小鼠，有一个突变的MMTV或TBLV LTR上游的c-myc应提供信息LTR的变化是否影响整合位点的选择或刺激c-myc表达的能力。这些结果应阐明有利于人类白血病发展的因素，并允许开发新的治疗策略。

The mouse mammary tumor virus (MMTV) induces primarily breast cancers in mice. However, some highly related MMTV strains (e.g., TBLV) induce T-cell tumors, but not mammary carcinomas. The major differences between (LTRs) at the ends of pro-viral DNA. These differences include (i) loss of negative regulatory elements (NREs) that suppress MMTV transcription in lymphoid tissues, including thymus, (ii) loss of the C-terminal one-third of the superantigen gene that is involved in MMTV transmission from lymphoid to mammary cells, and (iii) triplication of 62 bp flanking the LTR deletion. In this grant application, regions of the TBLV genome that are responsible for thymotropism will be assessed. First, the specific cell types infected by TBLV will be analyzed, and optimal routes of infection will be determined. Second, specific mutations in known NREs, the triplicated region of the sag open reading frame will be introduced into a mammotropic MMTV and tested for their ability to infect specific cell types and to cause leukemias. Third, the triplicated region shown to enhance MMTV transcription in T-cells will be analyzed for the binding of cellular transcription factors, and these factors will be identified. Fourth, if the LTR is not sufficient to reproduce the cell-type tropism and leukemogenicity of TBLV, we will construct chimeras between mammotropic and thymotropic strains of MMTV and test these chimeras for their ability to infect different cell types and induce disease. In the second specific aim, we will continue our studies to assess the role of specific TBLV integration sites in virally-induced leukemias. Previously identified TBLV integrations will be analyzed by PCR and by pulsed field gel electrophoresis. Integrations in the c-myc locus also will be assessed in leukemias induced by MMTV pro-viruses that have a truncated sag gene and lack the NREs, but also lack the specific triplicated region found in TBLV. These experiments and studies of transgenic mice that have a mutant MMTV or TBLV LTR upstream of c-myc should provide information about whether LTR changes affect integration site choice or the ability to stimulate c-myc expression. These results should elucidate the factors conducive for the development of human leukemia and permit the development of novel strategies for their treatment.