MOUSE MAMMARY TUMOR VIRUS AND DETERMINANTS OF LEUKEMOGENICITY

小鼠乳腺肿瘤病毒（MMTV）主要诱导小鼠乳腺癌。然而，一些高度相关的MMTV菌株（如TBLV）诱导t细胞肿瘤，但不诱导乳腺癌。在前病毒DNA末端的ltr之间的主要区别。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（NREs）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端三分之一的缺失，以及（iii） LTR缺失侧62 bp的三倍复制。在这项拨款申请中，将评估TBLV基因组中负责促胸腺功能的区域。首先，分析被TBLV感染的特定细胞类型，确定最佳感染途径。其次，将已知NREs中的特定突变，即凹陷开放阅读框的三复制区域引入嗜乳性MMTV，并测试其感染特定细胞类型和引起白血病的能力。第三，将分析t细胞中显示增强MMTV转录的三复制区域，以确定细胞转录因子的结合，并确定这些因子。第四，如果LTR不足以复制TBLV的细胞型亲和性和白血病性，我们将在嗜乳性和嗜胸性MMTV株之间构建嵌合体，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，以评估特异性TBLV整合位点在病毒诱导白血病中的作用。先前鉴定的TBLV整合将通过PCR和脉冲场凝胶电泳进行分析。在由MMTV前病毒诱导的白血病中，c-myc位点的整合也将被评估，这些病毒具有一个被切断的凹陷基因，缺乏NREs，但也缺乏TBLV中发现的特异性三复制区。这些针对在c-myc上游具有MMTV或TBLV LTR突变的转基因小鼠的实验和研究应该提供LTR变化是否影响整合位点选择或刺激c-myc表达能力的信息。这些结果应该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.