Laitinen J, Sistonen L, Alitalo K, Hölttä E
Department of Pathology, University of Helsinki, Finland.
J Cell Biochem. 1995 Jan;57(1):1-11. doi: 10.1002/jcb.240570102.
The activated c-Ha-rasVal12 oncogene is often involved in the genesis of human malignancies. We show here that in c-Ha-rasVal12 oncogene-transformed mouse NIH 3T3 fibroblasts the copy number and expression level of the mutant ras oncogene correlates with the degree of chromatin decondensation, as assessed by micrococcal nuclease (MNase) and DNase I digestion. MNase and DNase I analyses further revealed that the nucleosomal repeat lengths were different in the normal and ras oncogene-transformed cells, 162.3 bp and 178.1 bp, respectively. These chromatin changes were accompanied by alterations in the content of histone H1 zero. Furthermore, using DNase I as a probe, we discovered that serum stimulation of normal and transformed cells, synchronized by serum starvation, induces rapid reversible changes in the structure of bulk chromatin that may be linked to transcriptional activation. Our data thus indicate that cell transformation by ras is associated with specific changes in chromatin structure that make it more vulnerable, and prone to additional mutations characteristic of cancer development in vivo.
激活的c-Ha-rasVal12癌基因常参与人类恶性肿瘤的发生。我们在此表明，在c-Ha-rasVal12癌基因转化的小鼠NIH 3T3成纤维细胞中，突变型ras癌基因的拷贝数和表达水平与染色质解聚程度相关，这是通过微球菌核酸酶（MNase）和DNase I消化评估的。MNase和DNase I分析进一步揭示，正常细胞和ras癌基因转化细胞中的核小体重复长度不同，分别为162.3 bp和178.1 bp。这些染色质变化伴随着组蛋白H1零含量的改变。此外，使用DNase I作为探针，我们发现血清刺激经血清饥饿同步化的正常细胞和转化细胞，会诱导整体染色质结构的快速可逆变化，这可能与转录激活有关。因此，我们的数据表明，ras介导的细胞转化与染色质结构的特定变化相关，这些变化使其更易受到影响，并易于发生体内癌症发展特有的其他突变。
