Stein G H, Atkins L, Beeson M, Gordon L
Exp Cell Res. 1986 Jan;162(1):255-60. doi: 10.1016/0014-4827(86)90443-x.
The mechanism for cessation of proliferation in density-inhibited quiescent human diploid fibroblasts (HDF) and serum-deprived quiescent HDF was compared in two ways. Density-inhibited HDF were fused to either replicating HDF or SV40-transformed HDF and DNA synthesis was measured in the resulting heterokaryons. DNA synthesis was inhibited in the replicating HDF nuclei in heterokaryons in a way that suggested that entry into S phase was blocked, but ongoing DNA synthesis was not inhibited. In contrast, DNA synthesis was induced in the quiescent nuclei in heterokaryons formed with SV40-transformed HDF. Previous experiments had shown that serum-deprived HDF also behave in this way in heterokaryons. To test this similarity further, we examined the inhibitory activity of cell membranes prepared from both types of quiescent HDF. We found that both types of quiescent HDF contain DNA synthesis-inhibitory activity that is (1) effective on replicating HDF; (2) ineffective on SV40-transformed HDF; (3) sensitive to heat and trypsin. Thus, these results support the hypothesis that both density-inhibited HDF and serum-deprived HDF share a common mechanism for arrest in G1 phase. They also suggest that a membrane-bound protein plays a role in the inhibition of DNA synthesis in quiescent HDF.
采用两种方法比较了密度抑制的静止人二倍体成纤维细胞（HDF）和血清剥夺的静止HDF中增殖停止的机制。将密度抑制的HDF与正在复制的HDF或SV40转化的HDF融合，并在所得的异核体中测量DNA合成。异核体中正在复制的HDF细胞核中的DNA合成受到抑制，这种抑制方式表明进入S期受阻，但正在进行的DNA合成未受抑制。相反，在与SV40转化的HDF形成的异核体中，静止细胞核中的DNA合成被诱导。先前的实验表明，血清剥夺的HDF在异核体中也表现出这种行为。为了进一步检验这种相似性，我们检测了从两种类型的静止HDF制备的细胞膜的抑制活性。我们发现，两种类型的静止HDF都含有DNA合成抑制活性，该活性（1）对正在复制的HDF有效；（2）对SV40转化的HDF无效；（3）对热和胰蛋白酶敏感。因此，这些结果支持了以下假设：密度抑制的HDF和血清剥夺的HDF在G1期停滞具有共同机制。它们还表明，一种膜结合蛋白在静止HDF的DNA合成抑制中起作用。
