STRUCTURAL AND FUNCTIONAL ANALYSIS OF ENDOGENOUS PROVIRUSES OF MICE

小鼠基因组包含至少50个拷贝的小鼠白血病 病毒(MuLV)相关的DNA，其中大部分是有缺陷的。 不同感染性和缺陷性小鼠白血病病毒的重组 序列导致产生新的MuLV，包括 淋巴瘤性水貂细胞病灶形成(MCF)病毒。主 该项目的目标是：1)研究结构和规则 内源性缺陷MuLV前病毒DNA的表达；2) 研究重组MCF病毒的产生；3)鉴定 有助于MCF MuLV致白血病的序列。 内源性MCF env相关基因全长(8.4 kb)转录本 前病毒在自身免疫性胸腺组织中高表达 小鼠品系，但在非自身免疫品系中检测不到。 NZB在生命的第一天就检测到了8.4kb的RNA物种 小鼠，之前有自身免疫性疾病的临床表现。这个 数据表明，内源性MCF的表达与 DNA在自身免疫和非自身免疫中受到不同的调控 自身免疫的小鼠品系。 构建了MCF LTR特异性DNA探针，用于鉴定 MuLV提供可以捐赠LTR序列来产生 重组MCF MULV。两个潜在的LTR祖细胞是 检测到；一个包含异嗜性环境相关序列和 在染色体上被定位为可诱导的、内源性的 异嗜性MuLV基因座，Bxv-1；第二个特征是 与MCF相关的新内源性MuLV前病毒 MuLV。后者的DNA在基因组中是保守的 近亲繁殖的老鼠和几只野生老鼠。 整合酶基因在MCF诱导中的作用研究 胸腺瘤，一段2.7kb的DNA片段，包含3‘Pol区 导致白血病的MCF13被一个类似的片段取代 来自非白血病的MCF111AMuLV DNA。重组人 从转基因研究中获得的病毒被注射到 新生AKR小鼠检测MCF病毒基因组 用取代的整合酶保留其致白血病能力 吉恩。肿瘤的发展被推迟了，而且 胸腺瘤减少了50%。这些结果表明， 整合酶基因参与了MCF病毒的致白血病作用。

Mouse genome contains at least 50 copies of murine leukemia viral (MuLV)-related DNAs, the majority of which are defective. Recombination between different infectious and defective MuLV sequences results in the generation of novel MuLVs including lymphomagenic mink cell focus-forming (MCF) viruses. The main goals of this project are: 1) to study the structure and regulation of expression of endogenous defective MuLV proviral DNAs; 2) to study generation of recombinant MCF viruses; and 3) to identify sequences contributing to leukemogenicity of MCF MuLVs. Full-length (8.4 kb) transcripts of endogenous MCF env-related proviruses were highly-expressed in thymus tissues of autoimmune mouse strains but were not detectable in nonautoimmune strains. The 8.4 kb RNA species was detected from day 1 of life in NZB mice, prior to clinical manifestations of autoimmune disease. The data indicates that the expression of endogenous MCF-related DNAs is regulated differently in autoimmune versus non- autoimmune mouse strains. An MCF LTR-specific DNA probe was constructed to identify MuLV proviruses which could donate LTR sequences to generate recombinant MCF MuLVs. Two potential LTR-progenitors were detected; one contained xenotropic env-related sequences and was chromosomally mapped as the inducible, endogenous xenotropic MuLV locus, Bxv-1; the second was characterized as a novel endogenous MuLV provirus which was related in env to MCF MuLVs. The latter MuLV DNA was conserved in the genomes all inbred and several wild mice. To study the contribution of the integrase gene in MCF-induced thymomas, a 2.7 kb DNA segment containing the 3' pol region of leukemogenic MCF13 was substituted by an analogous segment from non-leukemogenic MCF111A MuLV DNA. The recombinant virus obtained from transfection studies was injected into newborn AKR mice to test whether the MCF viral genome retained its leukemogenic potential with the substituted integrase gene. Tumor development was delayed and the incidence of thymomas was reduced by 50%. These results suggest that the integrase gene contributes to leukemogenicity of MCF viruses.