Imai S, Saito F, Ikeuchi T, Segawa K, Takano T
Department of Microbiology, Keio University School of Medicine, Tokyo, Japan.
Mech Ageing Dev. 1993 Jun;69(1-2):149-58. doi: 10.1016/0047-6374(93)90079-7.
A human diploid fibroblast strain MRC-5 was transfected with a replication origin-defective early region of SV40 containing the gene of large T antigen, and 48 clones of T antigen-transformed MRC-5 were isolated. Although T antigen prolonged the lifespan of MRC-5, all the transformed clones were still mortal. From two of the transformed MRC-5 clones, eight independent immortalized clones were obtained in triple experiments of immortalization. The transformed phenotypes of immortalized clones were widely varied and did not always retain those of the parental pre-immortalized clones. The immortalization occurred at the frequency of about 1-3 x 10(-7)/cell. From cell number and population doubling time of the immortalized clones, the immortalization was estimated to occur in or just before the crisis of parental mortal cells. The decreases of modal chromosome numbers and the loss of chromosomes 5 and 10 were found to be common in three independent immortalized clones examined. Thus, the escape from the cellular aging process seemed to be caused by certain genetic events including the loss of chromosomes at the end of lifespan in T antigen-transformed human diploid cells.
用人二倍体成纤维细胞系MRC-5转染含大T抗原基因的SV40复制起点缺陷型早期区域，分离出48个T抗原转化的MRC-5克隆。尽管T抗原延长了MRC-5的寿命，但所有转化克隆仍然是有限寿命的。在三次永生化实验中，从两个转化的MRC-5克隆中获得了八个独立的永生化克隆。永生化克隆的转化表型差异很大，并不总是保留亲代永生化前克隆的表型。永生化发生的频率约为1-3×10(-7)/细胞。从永生化克隆的细胞数量和群体倍增时间估计，永生化发生在亲代有限寿命细胞的危机期或危机期之前。在所检测的三个独立永生化克隆中，发现众数染色体数目的减少以及5号和10号染色体的丢失很常见。因此，在T抗原转化的人二倍体细胞中，似乎是某些遗传事件导致了细胞衰老过程的逃逸，这些事件包括在寿命末期染色体的丢失。
