期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：11
页码：4937-4941
DOI：10.1073/pnas.74.11.4937
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have recently shown that, after the histones and most of the nonhistone proteins are gently removed from HeLa metaphase chromosomes, the chromosomal DNA is still highly organized and relatively compact. The structure of these histone-depleted chromosomes is due to the presence of a number of nonhistone proteins that form a central scaffold that retains the approximate size and shape of intact chromosomes and to which the DNA is attached, predominantly forming loops. We now demonstrate that the protein scaffold may be isolated independently of the DNA by treating HeLa chromosomes with micrococcal nuclease before removing the histones. The chromosomal scaffolds may be isolated by sucrose density gradient centrifugation as a well-defined peak that is stable in 2 M sodium chloride, but is dissociated by treatment with proteases, 4 M urea, or 0.1% sodium dodecyl sulfate. Polyacrylamide gel electrophoresis reveals that the protein content of scaffold preparations is identical to that of histone-depleted chromosomes. Fluorescence microscopy of purified scaffolds in isolation buffer shows that the particles still possess the familiar chromosome morphology. When the scaffolds are examined in the electron microscope, a fibrous structure with the approximate size and shape of intact, paired chromatids is seen. Less than 0.1% of the chromosomal DNA and virtually no histones are associated with the purified scaffold structures.
