Islam M Q, Szpirer J, Szpirer C, Islam K, Dasnoy J F, Levan G
Department of Genetics, University of Gothenburg, Sweden.
J Cell Sci. 1989 Feb;92 ( Pt 2):147-62. doi: 10.1242/jcs.92.2.147.
Cell hybrids between malignant mouse hepatoma cells and normal rat fibroblasts with approximately one set of chromosomes from each parent exhibited remarkable karyotypic stability. Most chromosomes of both parents were retained even after prolonged culture in vitro. Normally, such hybrids showed suppression of the transformed phenotype and formed no colonies in soft agar. However, two hybrids, BS140 and BS181, formed a few colonies in soft agar when many cells were seeded, and also occasional foci of cells were detected piling up in monolayer cell cultures. We isolated soft agar colonies (a-subclones) and sub-clones from foci (h-subclones) of both hybrids, and, as a control, subclones of cells from random areas without foci of one hybrid (BS181 p-subclones). When tested for soft agar growth, cells from the a- and h-subclones of both BS140 and BS181 formed colonies at frequencies comparable to the malignant mouse hepatoma parent, whereas the control cells of the BS181 p-subclones (like the normal rat parental cells) yielded no soft agar colonies. All the cell lines were subjected to detailed karyotype analysis in G-banding, which resulted in the finding that cells from the original BS140 hybrid contained at least one copy of each rat chromosome, whereas BS140 a- and h-subclones had lost both copies of rat chromosome 5. Similarly, the original BS181 hybrid contained at least one copy of each rat chromosome, whereas BS181 a- and h-subclones displayed a deletion of the segment q22-23 of rat chromosome 5. In contrast, the control BS181 p-subclones contained one or two copies of non-deleted rat chromosome 5. The conclusion is that a gene for the suppression of anchorage independence is located in the segment 5q22-23. We propose to call this gene SAI1 (for suppression of anchorage independence). Using Southern blotting, we tested whether any of several gene probes, known to correspond to DNA sequences in rat chromosome 5, were homologous to sequences in the deletion. Only one probe, corresponding to the active alpha1-interferon gene, was shown to be located within the deletion. Hence, the SAI1 gene is closely linked to the alpha 1-interferon gene, and might be identical to this locus.
恶性小鼠肝癌细胞与正常大鼠成纤维细胞之间的细胞杂种，各自带有来自亲本的大约一组染色体，表现出显著的核型稳定性。即使在体外长时间培养后，双亲的大多数染色体仍被保留。正常情况下，这类杂种显示出转化表型受到抑制，在软琼脂中不形成集落。然而，两个杂种细胞系BS140和BS181，在接种大量细胞时能在软琼脂中形成一些集落，并且在单层细胞培养中也偶尔检测到细胞灶堆积现象。我们从这两个杂种细胞系的软琼脂集落（α-亚克隆）和细胞灶（h-亚克隆）中分离出亚克隆，作为对照，还从其中一个杂种细胞系（BS181 p-亚克隆）没有细胞灶的随机区域分离出细胞亚克隆。当检测软琼脂生长情况时，BS140和BS181的α-亚克隆和h-亚克隆细胞形成集落的频率与恶性小鼠肝癌亲本相当，而BS181 p-亚克隆的对照细胞（如同正常大鼠亲本细胞）未产生软琼脂集落。所有细胞系都进行了详细的G显带核型分析，结果发现原始的BS140杂种细胞系的细胞含有大鼠每条染色体的至少一个拷贝，而BS140的α-亚克隆和h-亚克隆失去了大鼠5号染色体的两个拷贝。同样，原始的BS181杂种细胞系含有大鼠每条染色体的至少一个拷贝，而BS181的α-亚克隆和h-亚克隆显示大鼠5号染色体q22 - 23区段缺失。相比之下，对照的BS181 p-亚克隆含有一条或两条未缺失的大鼠5号染色体。结论是，抑制锚定非依赖性的基因位于5q22 - 23区段。我们提议将这个基因命名为SAI1（抑制锚定非依赖性）。使用Southern印迹法，我们检测了几个已知对应大鼠5号染色体DNA序列的基因探针，是否与缺失区段中的序列同源。只有一个对应活性α1-干扰素基因的探针显示位于缺失区段内。因此，SAI1基因与α1-干扰素基因紧密连锁，可能与该位点相同。
