Rao B J, Brahmachari S K, Rao M R
J Biol Chem. 1983 Nov 25;258(22):13478-85.
Pachytene nuclei were isolated from rat testes by the unit gravity sedimentation technique and contained histone variants H1a, H1t, TH2A, TH2B, and X2 in addition to the somatic histones H1bde, H1c, H2A, H2B, H3, and H4. The basic organization of the pachytene chromatin namely the nucleosome repeat length and the accessibility to micrococcal nuclease, was similar to that of rat liver interphase chromatin. However, when digested by DNase I, the susceptibility of pachytene chromatin was 25% more than liver chromatin under identical conditions. Nucleosome core particles were isolated from both liver and pachytene nuclei and were characterized for their DNA length and integrity of the nucleoprotein on low ionic strength nucleoprotein gels. While liver core particles contained all the somatic histones H2A, H2B, H3, and H4, in the pachytene core particles, histone variants TH2A, X2, and TH2B had replaced nearly 60% of the respective somatic histones. A comparison of the circular dichroism spectra obtained for pachytene and liver core particles indicated that the pachytene core particles were less compact than the liver core particles. Studies on the thermal denaturation properties of the two types of core particles revealed that the fraction of the pachytene core DNA melting at the premelting temperature region of 55-60 degrees C was significantly higher than that of the liver core DNA.
通过单位重力沉降技术从大鼠睾丸中分离出粗线期细胞核，其中除了含有体细胞组蛋白H1bde、H1c、H2A、H2B、H3和H4外，还含有组蛋白变体H1a、H1t、TH2A、TH2B和X2。粗线期染色质的基本组织，即核小体重复长度和对微球菌核酸酶的可及性，与大鼠肝脏间期染色质相似。然而，在相同条件下用DNase I消化时，粗线期染色质的敏感性比肝脏染色质高25%。从肝脏和粗线期细胞核中都分离出了核小体核心颗粒，并在低离子强度核蛋白凝胶上对其DNA长度和核蛋白完整性进行了表征。肝脏核心颗粒含有所有体细胞组蛋白H2A、H2B、H3和H4，而在粗线期核心颗粒中，组蛋白变体TH2A、X2和TH2B几乎取代了各自体细胞组蛋白的60%。对粗线期和肝脏核心颗粒获得的圆二色光谱的比较表明，粗线期核心颗粒比肝脏核心颗粒的结构更松散。对这两种类型核心颗粒的热变性特性的研究表明，在55-60℃的预熔温度区域熔化的粗线期核心DNA的比例明显高于肝脏核心DNA。
