中间丝波纹蛋白在细胞,端粒维持和细胞不死化中的作用.ppt

Vimentin Positive (Vim+) Vimentin Negative (Vim- ) Cells Passage* Cells Passage* Vim+/+ 10-12 Vim-/- 10-12 clones: clones: A4 low III7E low A4 high III7E high B7 low III8F low B7 high III8F high IV2E low IV2E high IV8B low IV8B high *low = passage 20-30, high = passage 200-500; cells below passage 10-12 (“crisis”) are primary cells (pr), those above passage 12 are spontaneously immortalized (im) cells. Immortalized vimentin-positive and vimentin-negative cells were expanded into the clones by limiting dilution method. * Potential role of the intermediate filament protein vimentin in telomere maintenance and spontaneous cell immortalization. Jian-Ping Lu, Genrich V. Tolstonog and Peter Traub Abstract Similar to knockout of telomerase RNA, knockout of the vimentin gene severely impairs spontaneous immortalization of primary mouse embryo fibroblasts. Therefore, the expression and activity of telomerase in primary and immortalized embryo fibroblasts from wild-type (Vim+/+) and vimentin knockout (Vim-/-) mice were studied. While the primary Vim+/+ fibroblasts exhibited telomerase activity and progressively reduced their growth potential during serial transfer, passed through a growth minimum around passage 12 and, as immortalized cells, resumed faster growth, the primary Vim-/- fibroblasts did not show detectable telomerase activity, cut down their growth rate much earlier and immortalized at an extremely low rate. In primary Vim-/- cells at the growth minimum, telomere chromatin was strongly decondensed and mainly associated with the nucleoli, in contrast to primary Vim+/+ cells in which the telomeres were less decondensed and localized predominantly at the nuclear periphery. Although the telomerase activity was significantly