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：4867-4871
DOI：10.1073/pnas.74.11.4867
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：We have analyzed the DNA generated upon treatment of oviduct nuclei with pancreatic DNase I (deoxyribonucleate 3'-oligonucleotidohydrolase; EC 3.1.4.6 ), with cDNA copies of specific mRNA sequences to study the structure and organization of transcriptionally active genes in chromatin. In this report we examine the kinetics of digestion of three classes of genes in the oviduct which are transcribed at significantly different rates. Our results indicate that the ovalbumin genes appear to be organized by chromatin proteins in such a way that they are rendered exceedingly sensitive to digestion by DNase I. This sensitivity is not observed in the liver, a tissue in which these genes are transcriptionally inert. Furthermore, the transcriptionally inactive globin genes in the oviduct are not selectively sensitive to nuclease attack and are digested 5 times more slowly in the ovalbumin genes in this tissue. In addition, we have examined the accessibility of a complex subset of genes that are rarely represented in the mRNA and are likely to be transcribed at a frequency orders of magnitude below that of the ovalbumin gene. Comparison of the accessibility of these sequences with that of the ovalbumin gene indicates that these two subsets of genes are recognized and cleaved by DNase I at similar rates. These results suggest that the maintenance of an active conformation about specific genes does not reflect the polymerase distribution about these genes. This active conformation is therefore not confined to sequences actively engaged in the transcription process and may reflect the structure about a subpopulation of the genome which represents the transcriptional potential of a given cell type.
关键词：chromatin structure ; transcription ; DNA reassociation
