DNA-CONDENSING AND CHROMATIN-CONDENSING PROPERTIES OF RAT TESTES HLA AND HIT COMPARED TO THOSE OF RAT-LIVER HLBDEC - HLT IS A POOR CONDENSER OF CHROMATIN
DNA-CONDENSING AND CHROMATIN-CONDENSING PROPERTIES OF RAT TESTES HLA AND HIT COMPARED TO THOSE OF RAT-LIVER HLBDEC - HLT IS A POOR CONDENSER OF CHROMATIN
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DOI：
10.1021/bi00048a025
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发表时间：
1995-12-05
期刊：
影响因子：
2.9
通讯作者：
RAO, MRS
中科院分区：
文献类型：
--
作者：
KHADAKE, JR;RAO, MRS
组蛋白H1 a和H1 t是存在于哺乳动物精子发生粗线期间隔的两种主要的连接体组蛋白变体。从大鼠睾丸中分离的这两种变体的DNA和染色质凝聚特性进行了研究，并与大鼠肝脏中的那些进行了比较。为此目的，使用浴酸和盐提取程序从各自的组织中纯化组蛋白H1亚型。圆二色性研究表明，分离期间的酸暴露影响球状结构域（在1 M NaCl存在下）和C-末端双螺旋尾（在60%三氟乙醇存在下）的α-螺旋结构。大鼠寡核小体DNA的缩合，如通过圆二色性光谱测量的，由盐提取的组蛋白H1是至少10倍，更有效地比缩合由酸提取的组蛋白H1。计算盐提取的组蛋白H1的位点大小为16-20个碱基对。在不同的组蛋白H1亚型中，体细胞组蛋白H1bdec具有最高的DNA凝聚性，其次是组蛋白H1 a和组蛋白H1 t。所有的盐提取的组蛋白浓缩大鼠寡核体DNA比线性pBR-322 DNA更有效，组蛋白H1bdec和H1 a浓缩组蛋白H1耗尽的染色质，从大鼠肝细胞核制备，具有相对相等的效率。另一方面，没有组蛋白H1耗尽的染色质与睾丸特异性组蛋白H1 t的凝聚。组蛋白H1 d（大鼠）和组蛋白H1 t（大鼠）的氨基酸序列的比较揭示了几个有趣的差异在C-末端的DNA结合基序的发生。一个引人注目的观察结果是组蛋白H1 d中存在八肽基序K（A）T（S）PKKA（S）K（T）K（A）的直接重复，而组蛋白H1 t中不存在。
Histones H1a and H1t are two major linker histone variants present at the pachytene interval of mammalian spermatogenesis. The DNA- and chromatin-condensing properties of these two variants isolated from rat testes were studied and compared with those from rat liver. For this purpose, the histone H1 subtypes were purified from the respective tissues using bath acid and salt extraction procedures, Circular dichroism studies revealed that acid exposure during isolation affects the alpha-helical structure of both the globular domain (in the presence of 1 M NaCl) and the C-terminal lambda-tail (in the presence of 60% trifluoroethanol). The condensation of rat oligonucleosomal DNA, as measured by circular dichroism spectroscopy, by the salt-extracted histone H1 was at least 10 times more efficient than condensation by the acid-extracted histone H1. A site size of 16-20 base pairs was calculated for the salt-extracted histone H1. Among the different histone H1 subtypes, somatic histone H1bdec had the highest DNA-condensing property, followed by histone H1a and histone H1t. All the salt-extracted histones condensed rat oligonucleosomal DNA more efficiently than linear pBR-322 DNA, Histones H1bdec and H1a condensed histone H1-depleted chromatin, prepared from rat liver nuclei, with relatively equal efficiency. On the other hand, there was no condensation of histone H1-depleted chromatin with the testes specific histone H1t. A comparison of the amino acid sequences of histone H1d (rat) and histone H1t (rat) revealed several interesting differences in the occurrence of DNA-binding motifs at the C-terminus. A striking observation is the presence of a direct repeat of an octapeptide motif K(A)T(S)PKKA(S)K(T)K(A) in histone H1d that is absent in histone H1t.