Topic
Nucleolar chromatin
About: Nucleolar chromatin is a research topic. Over the lifetime, 170 publications have been published within this topic receiving 6776 citations.
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TL;DR: It is shown, by protein biochemical analysis, that the ubiquitously expressed subtype H1x is enriched in the micrococcal nuclease‐resistant part of chromatin and that, although it shares common features with H1°, its expression is differentially regulated, since, in contrast to H 1°, growth arrest or induction of differentiation did not induce an accumulation of H1X.
45 citations
TL;DR: It is indicated that pKi-67 dynamically alters the nature of the interaction with chromatin structure during the cell cycle, which is closely related to the reformation process of the interphase nucleolar chromatin.
45 citations
TL;DR: It is concluded that H1 organizes and maintains an extensive protein-protein interaction network in the nucleolus required for nucleolar structure and integrity.
44 citations
TL;DR: Examination of amplified nucleoli of Xenopus oocytes provides clear evidence that the transcriptionally active rRNA genes are confined to the fibrillar centers of the oocyte nucleoli and opens the possibility to analyze the protein composition of almost native, transcriptionally highly active nucleolar chromatin by immunofluorescence microscopy.
Abstract: An understanding of the functional organization of nucleoli, the sites of ribosome biosynthesis, is limited by the present uncertainty about the topological arrangement of the transcribing rRNA genes. Since studies with "standard" nucleoli from somatic cells produced conflicting results, we have examined the amplified nucleoli of Xenopus oocytes. These nucleoli are unique in that they contain high copy numbers of rRNA genes, are not attached to chromosomes, lack non-ribosomal DNA and can be examined in light microscopic spread preparations of nuclear contents. By immunostaining and confocal microscopy we show that in growing stage IV oocytes the sites of rDNA are surrounded by the dense fibrillar component. The rDNA is actively transcribed as revealed by BrUTP injection into oocytes and localization of components of the nucleolar transcription machinery (RNA polymerase I and the transcription factor UBF). At the ultrastructural level, the rDNA sites correlate with the fibrillar centers of amplified nucleoli fixed in situ. The results provide clear evidence that the transcriptionally active rRNA genes are confined to the fibrillar centers of the oocyte nucleoli and open the possibility to analyze the protein composition of almost native, transcriptionally highly active nucleolar chromatin by immunofluorescence microscopy.
43 citations
TL;DR: Aflatoxin B1, after metabolic activation either in vivo or in vitro, binds preferentially to the physiologically active regions of rat liver nucleolar chromatin, and that this binding specificity is largely lost after the removal of chromosomal proteins from the nucleoli.
Abstract: The literature on various isolated carcinogen-DNA adducts indicates clearly that the binding of chemical carcinogens to DNA is highly specific. Since DNA in eukaryotic cells is complexed with chromosomal proteins and organized into transcriptionally active and inactive chromatin, chemical carcinogens also might show binding specificities at the chromatin level. Using Escherichia coli RNA polymerase and the endogenous engaged RNA polymerase I as specific probes to monitor respectively the physiologically inactive and active nucleolar chromatin template function, this paper reports that aflatoxin B1, after metabolic activation either in vivo or in vitro, binds preferentially to the physiologically active regions of rat liver nucleolar chromatin, and that this binding specificity is largely lost after the removal of chromosomal proteins from the nucleoli.
42 citations