Weihe A, Schmidt G, von Mickwitz C U, Lindigkeit R
Acta Biol Med Ger. 1982;41(7-8):609-24.
Nonhistone proteins (NHPs) of salt-soluble chromatin (Chromatin S) and of the residual nuclei (Chromatin P) from rat liver and thymus were studied by SDS-polyacrylamide gel electrophoresis. The two chromatin fractions of the liver showed significant differences in their NHP patterns with most of the hnRNP and matrix proteins occurring in Chromatin P. In accordance with the low protein content of thymus nuclei, the corresponding thymus fractions exhibited electrophoretic patterns with a markedly lower amount of NHPs than in liver. Chromatin P from thymus, in contrast to the liver fraction, revealed only a very low content of hnRNP-specific proteins of molecular weight 30,000-40,000 (30 K to 40 K) (informosomal proteins) consistent with the significantly lower RNA content of thymus nuclei. In the region of the matrix proteins (60-75 K) Chromatin P showed only two bands of about 64 K and 73 K in thymus, whereas in liver five strong bands at 64 K, 66 K, 69 K, 73 K, and 75 K were found. RNase digestion was employed to discriminate hnRNP-specific protein from "real" chromosomal NHPs. At least about 65% and 25% of the NHPs from Chromatin P and S of liver, respectively, were found to be RNP-specific. The two chromatin fractions were further fractionated by sucrose gradient centrifugation and isopycnic banding in metrizamide. After centrifugation the main peaks, both of Chromatin S and P, contained only minor amounts of NHPs with a predominating protein of 38 K. By the centrifugation procedures described in this paper, a small subfraction of chromatin could be separated which was enriched in newly synthesized RNA, informosomal proteins, matrix- and other high molecular weight proteins. This subfraction might be related to transcriptionally active chromatin.
采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法，对大鼠肝脏和胸腺中盐溶性染色质（染色质S）及残留细胞核（染色质P）的非组蛋白进行了研究。肝脏的两种染色质组分在非组蛋白图谱上表现出显著差异，大多数不均一核核糖核蛋白（hnRNP）和基质蛋白存在于染色质P中。鉴于胸腺细胞核的蛋白质含量较低，相应的胸腺组分所呈现的电泳图谱显示，其非组蛋白的含量明显低于肝脏中的含量。与肝脏组分不同，胸腺的染色质P中，分子量为30000 - 40000（30K至40K）的hnRNP特异性蛋白（信息体蛋白）含量极低，这与胸腺细胞核中RNA含量显著较低相一致。在基质蛋白区域（60 - 75K），胸腺染色质P仅显示出两条约64K和73K的条带，而在肝脏中则发现了64K、66K、69K、73K和75K的五条强条带。采用核糖核酸酶消化法，将hnRNP特异性蛋白与“真正的”染色体非组蛋白区分开来。结果发现，肝脏染色质P和S中至少分别约65%和25%的非组蛋白是RNP特异性的。通过蔗糖梯度离心和在甲泛影酰胺中的等密度沉降，对这两种染色质组分进一步进行分级分离。离心后，染色质S和P的主峰中均仅含有少量非组蛋白，其中占主导的蛋白分子量为38K。通过本文所述的离心程序，可分离出一小部分染色质亚组分，该亚组分富含新合成的RNA、信息体蛋白、基质蛋白和其他高分子量蛋白。该亚组分可能与转录活性染色质有关。
