Carmon Y, Czosnek H, Nudel U, Shani M, Yaffe D
Nucleic Acids Res. 1982 May 25;10(10):3085-98. doi: 10.1093/nar/10.10.3085.
Cultures of a rat myogenic cell line were used to examine the question of whether in proliferating precursor cells genes which are programmed to be expressed later in development, in the same cell lineage, differ in DNAase I sensitivity from genes which are never expressed in these cells. Nuclei isolated from proliferating mononucleated myoblasts, differentiated cultures containing multinucleaged fibers, and rat brain, were treated with DNAase I. The sensitivity of the genes coding for the muscle-specific alpha-actin, myosin light chain 2 and the nonmuscle beta-actin was measured by blot hybridization of nuclear DNA with the corresponding cloned cDNA and genomic DNA probes. The sensitivity of these genes was compared to that of a gene not expressed in the muscle tissue. The results showed that in the muscle precursor cells, the potentiality of tissue-specific genes to be expressed is not reflected in DNAase I sensitivity. The changes which render these genes preferentially sensitive to DNAase I take place during the transition to terminal differentiation. The results showed also that the region of DNAase I sensitivity of the alpha-actin gene in the differentiated cells ends between 40 to 700 bp 5' to the structural gene. No DNAase I hypersensitive site was detected 5' to the alpha-actin gene.
利用大鼠成肌细胞系的培养物来研究在增殖的前体细胞中，那些在发育后期、在同一细胞谱系中按程序表达的基因，其对DNA酶I的敏感性是否与这些细胞中从未表达的基因不同。从增殖的单核成肌细胞、含有多核纤维的分化培养物以及大鼠脑中分离出细胞核，用DNA酶I处理。通过用相应的克隆cDNA和基因组DNA探针与核DNA进行印迹杂交，来测定编码肌肉特异性α-肌动蛋白、肌球蛋白轻链2和非肌肉β-肌动蛋白的基因的敏感性。将这些基因的敏感性与肌肉组织中未表达的一个基因的敏感性进行比较。结果表明，在肌肉前体细胞中，组织特异性基因的表达潜能在DNA酶I敏感性方面并未体现出来。使这些基因对DNA酶I优先敏感的变化发生在向终末分化的转变过程中。结果还表明，在分化细胞中，α-肌动蛋白基因对DNA酶I敏感的区域在结构基因5'端40至700 bp之间结束。在α-肌动蛋白基因5'端未检测到DNA酶I超敏感位点。
