Nose K, Ishino K, Shibanuma M
Department of Microbiology, Showa University School of Pharmaceutical Sciences, Tokyo, Japan.
Biol Pharm Bull. 1998 Sep;21(9):911-3. doi: 10.1248/bpb.21.911.
The telomere is a specialized chromatin structure composed of unique repetitive DNA sequences and specific nuclear proteins. Telomere sequence-binding activity was measured by a mobility shift assay using nuclear extract from normal human fibroblasts. The specific binding activity to the telomere sequence increased in cells that were in a senescence state compared to that in cells at early population doublings. Treatment of cells with tumor promoting phorbol ester TPA induced an increase in the telomere sequence binding activity of nuclear extract in young cells, but the increase was marginal in senescent cells. DNA-damaging N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) also increased the telomere sequence binding activity in young cells, but not in senescent cells. As a reference, we measured the binding activity to NFkB sequence. It was activated by TPA or okadaic acid, but was not affected by MNNG or in senescence. The increase in telomere sequence-binding activity seemed to depend on activation of tyrosine phosphorylation, since an inhibitor of Tyr-kinase abolished the increase in telomere-binding activity. The molecular weight of the major binding factor in the normal human fibroblasts was approximately 32 kDa which is different from that of the telomere-associated protein, TRF-1.
端粒是一种由独特的重复DNA序列和特定核蛋白组成的特殊染色质结构。通过使用正常人成纤维细胞核提取物的迁移率变动分析来测量端粒序列结合活性。与早期群体倍增的细胞相比，处于衰老状态的细胞中端粒序列的特异性结合活性增加。用促肿瘤佛波酯TPA处理细胞可诱导年轻细胞核提取物的端粒序列结合活性增加，但衰老细胞中的增加幅度较小。DNA损伤剂N-甲基-N'-硝基-N-亚硝基胍（MNNG）也可增加年轻细胞中的端粒序列结合活性，但衰老细胞中则不然。作为对照，我们测量了对NFkB序列的结合活性。它被TPA或冈田酸激活，但不受MNNG影响，也不受衰老影响。端粒序列结合活性的增加似乎取决于酪氨酸磷酸化的激活，因为酪氨酸激酶抑制剂可消除端粒结合活性的增加。正常人成纤维细胞中主要结合因子的分子量约为32 kDa，这与端粒相关蛋白TRF-1不同。
