CHROMOSOME TRANSLOCATED ONCOGENES AND NEOPLASIA

禽逆转录病毒转化的鼠和人细胞类似物 基因（c-myc）与染色体易位直接相关 常见于鼠浆细胞瘤（t（12;15））和伯基特淋巴瘤 (t(8（14））。 我们建议继续并扩展我们的分子研究， myc基因激活对细胞转化的基础和后果。 小鼠浆细胞瘤中myc基因重排的不同分子靶点 （PCTs）将被定位，其结构和意义的myc 表达决心。 为此，我们最近确定了一本小说 一类具有易位断裂点的PCT聚集在c-myc的5'端， 改变myc表达的调节。 这些易位的位点 确定对正常的免疫系统重要的假定调节元件的位置， c-myc基因调控。 c-myc基因启动子的活性及其潜在的 增强子元件将通过它们驱动表达的能力来评估 融合基因（即，氯霉素乙酰转移酶或CAT）， 成纤维细胞和不同的淋巴细胞类型。 的染色质结构 转录活性和沉默的c-myc等位基因将与 进一步表征重要的调控区域。 修改后的myc基因将 稳定地整合到表达正常的 或截短的myc RNA。 对正常和隐性myc的影响 将确定启动子活动。 转染的和 内源性myc基因也将在这些转染的细胞中与 myc外显子和内含子特异性探针。 这些实验将使我们能够 研究调节myc表达潜在的顺式或反式系统。 转录和转录后机制的作用 将在各种淋巴肿瘤系中评估c-myc表达 携带破坏c-myc基因座的易位。 最后，鼠 含有激活的myc或人ras癌基因的逆转录病毒载体 将被引入到正常增殖的B细胞中， 生长因子依赖性分析。 （十）

The murine and human cellular analogues of an avian retroviral transforming gene (c-myc) have been directly associated with chromosome translocations commonly observed in murine plasmacytomas (t(12;15)) and Burkitt lymphomas (t(8;14)). We propose to continue and extend our studies of the molecular basis and consequences of myc gene activation for cell transformation. Different molecular targets for myc rearrangements in murine plasmacytomas (PCTs) will be localized and their structures and significance for myc expression determined. To this end, we have recently identified a novel class of PCTs with translocation breakpoints clustered 5' of c-myc which alter the regulation of myc expression. The site of these translocations define the locations of putative regulatory elements important for normal c-myc gene control. The activities of c-myc promoter and potential enhancer elements will be assessed by their ability to drive the expression of a fused gene (i.e., chloramphenicol acetyl transferase or CAT) in fibroblasts and different lymphoid cell types. The chromatin structures of transcriptionally active and silent c-myc alleles will be compared to further characterize important regulatory regions. Modified myc genes will be stably integrated into lymphoid tumor cells which express either normal or truncated myc RNAs. The resultant effect(s) on normal and cryptic myc promoter activities will be determined. The activity of transfected and endogenous myc genes will also be compared in these transfected cells with myc exon and intron specific probes. These experiments will allow us to investigate potential cis or trans systems for regulating myc expression. The contributions of transcriptional and post-transcriptional mechanisms for c-myc expression will be assessed in a variety of lymphoid tumor lines bearing translocations which disrupt the c-myc locus. Finally, murine retroviral vectors containing either activated myc or human ras oncogenes will be introduced into normal proliferating B cells and their effects on growth factor dependency analyzed. (X)