Identification of a growth-suppressing gene in normal human fibroblasts and mouse brain

哺乳动物的正常体细胞在有限数量的细胞分裂后停止在培养中分裂。这种现象被称为细胞衰老，由几个基因控制。当这些基因在细胞中失活时，它就获得了无限分裂和永生的可能性。遗传分析表明，在人类永生化细胞系中至少存在四个遗传互补组(A-D)。我们已经发现，通过微细胞介导的染色体转移导入人7号染色体可以特异性地诱导D组细胞系衰老。然后，我们以小鼠A9细胞为背景，制作了一组辐射杂交细胞。对杂交种进行了FISH分析和带有STS标记的聚合酶链式反应，以确定人类7号染色体片段是如何整合到小鼠A9基因组上的。在这些杂交种中，我们选择了一个只含有2-3Mb人类DNA的克隆，可以诱导D组细胞系衰老。我们从这个克隆中回收了人的DNA，并将其作为探针定位了人类7号染色体上可能的衰老基因。这些定位数据为我们鉴定该基因提供了有用的数据。

Normal somatic cells in mammals stop dividing in culture after a limited number of cell division. This phenomenon is called cellular senescence and governed by several genes. When these genes are inactivated in a cell, it acquires potential to divide indefinitely and immortalize. Genetic analysis revealed that there exist at least four genetic complementation groups (A-D) in immortal human cell lines. We have found that introduction of human chromosme 7 by microcell-mediated chromosome transfer specifically induces senescence in cell lines belonging to group D.Then we made a panel of radiation hybrids under the backgroud of mouse A9 cells. The hybrids were characterized by FISH analysis and PCR with STS markers to determine how fragments of human chromosme 7 are integrated on mouse A9 genome. Of these hybrids, we selected a clone that contains only 2-3 Mb human DNA and can induce senescence in group D cell lines. We rescued human DNA from this clone and used it as a probe to map the putative senescence gene on human chromosme 7. The mapping data are useful for us to identify the gene.