Smith J C, Stiles C D
Proc Natl Acad Sci U S A. 1981 Jul;78(7):4363-7. doi: 10.1073/pnas.78.7.4363.
BALB/c 3T3 mouse cells exposed briefly to platelet-derived growth factor (PDGF) become "competent" to replicate their DNA and divide. When cells are treated with PDGF and then fused to untreated cells, the resulting heterokaryons become competent to replicate their DNA. Cytoplasts derived from PDGF-treated cells are also able to transfer the growth response to untreated cells. After cytoplasmic transfer to another cell, the strength of the PDGF-induced mitogenic signal is attenuated by a factor roughly proportional to the increase in total cytoplasmic volume. When RNA synthesis is blocked during PDGF treatment, cells do not acquire the capacity to transfer the PDGF growth signal to untreated cells. By contrast, exposure to cycloheximide during PDGF treatment has no effect. These observations suggest that cytoplasmic transfer of the growth response to PDGF (competence) is mediated by a PDGF-induced stable RNA rather than by PDGF itself or a PDGF--receptor complex. The onset of DNA synthesis in PDGF--control heterokaryons occurs a minimum of 11 hr after cell fusion. Thus the substance that is transferred in these cell fusions is not directly involved in DNA synthesis; rather, it seems to trigger a sequence of events culminating in DNA synthesis.
短暂暴露于血小板衍生生长因子（PDGF）的BALB/c 3T3小鼠细胞变得“有能力”复制其DNA并进行分裂。当细胞用PDGF处理后再与未处理的细胞融合时，产生的异核体变得有能力复制其DNA。源自PDGF处理细胞的胞质体也能够将生长反应传递给未处理的细胞。在将细胞质转移到另一个细胞后，PDGF诱导的促有丝分裂信号的强度会被一个大致与总细胞质体积增加成比例的因子减弱。当在PDGF处理期间RNA合成被阻断时，细胞不会获得将PDGF生长信号传递给未处理细胞的能力。相比之下，在PDGF处理期间暴露于环己酰亚胺没有影响。这些观察结果表明，对PDGF的生长反应的细胞质转移（能力）是由PDGF诱导的稳定RNA介导的，而不是由PDGF本身或PDGF-受体复合物介导的。在PDGF控制的异核体中，DNA合成的起始在细胞融合后至少11小时发生。因此，在这些细胞融合中转移的物质并不直接参与DNA合成；相反，它似乎触发了一系列最终导致DNA合成的事件。
