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: The results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA topoisomerase I are located together.
73 citations
TL;DR: It is shown that nucleolar segregation is spatially separated and temporally delayed from the rest of the genome during mid-anaphase and coincides with the FEAR release of Cdc14p, demonstrating that one function of the Fear network is to promote segregation of repetitive nucleolar chromatin during mid the anaphase.
Abstract: In order to transmit a full genetic complement cells must ensure that all chromosomes are accurately split and distributed during anaphase. Chromosome XII in S. cerevisiae contains the site of nucleolar assembly, a 1-2Mb array of rDNA genes named RDN1. Cdc14p is a conserved phosphatase, essential for anaphase progression and mitotic exit, which is kept inactive at the nucleolus until mitosis. In early anaphase, the FEAR network (Cdc Fourteen Early Anaphase Release) promotes the transient and partial release of Cdc14p from the nucleolus. The putative role of Cdc14p released by the FEAR network is thought to be the stimulation of full Cdc14p release by activation of the GTPase-driven signaling cascade (the Mitotic Exit Network or MEN) that ensures mitotic exit. Here, we show that nucleolar segregation is spatially separated and temporally delayed from the rest of the genome. Nucleolar segregation occurs during mid-anaphase and coincides with the FEAR release of Cdc14p. Inactivation of FEAR delays nucleolar segregation until late anaphase, demonstrating that one function of the FEAR network is to promote segregation of repetitive nucleolar chromatin during mid-anaphase.
71 citations
TL;DR: The modified thermal stability of nucleolar chromatin was found to be caused by its content of RNA which partially destabilized the DNA-histone interactions, and the striking structural differences between these two chromatin types do not appear to be reflected in their protein contents at the present level of resolution.
69 citations
TL;DR: Transcriptionally active chromatin from peripheral amplified nucleoli of lampbrush-chromosome stage oocytes of Xenopus laevis was dispersed and spread in various solutions of low salt concentrations and examined by electron microscopy, demonstrating the existence of both strands with obviously homogeneous repeating units and strands with intra-axial heterogeneity of rDNA subunits.
Abstract: Transcriptionally active chromatin from peripheral amplified nucleoli of lampbrush-chromosome stage oocytes of Xenopus laevis was dispersed and spread in various solutions of low salt concentrations (including some with additions of detergents) and examined by electron microscopy. Nucleolar material from oocytes of animals with normal (2-nu) and mutant (1-nu) genetical constitution of nucleolus organizers was compared. Histograms showing the distributions of the lengths of matrix units, apparent spacer intercepts, and the total repeating units of the rDNA containing chromatin axes revealed a significant degree of heterogeneity, with indications of subclasses and predominant repeat unit size classes of 3.3 and 3.8 μm length. The correspondence of matrix unit length to the molecular weight of the first stable product of rDNA transcription was studied using gel electrophoresis of labelled pre-rRNA under non-denaturing and denaturing conditions. Evaluations of individual strands of nucleolar chromatin further demonstrated the existence of both (i) strands with obviously homogeneous repeating units and (ii) strands with intra-axial heterogeneity of rDNA subunits. “Preludecomplexes”, i.e. groups of transcriptional complexes in apparent spacer intercepts, were not infrequently noted. The data are compared with the measurements of lengths of repeating units in fragments of rDNA obtained by digestion with EcoRI endonuclease as described by Morrow et al. (1974) and Wellauer et al. (1974, 1976a, b). The results are discussed in relation to problems of variations in the modes of arrangement of the pre-rRNA genes, the state of packing of rDNA during transcription, and possible mechanisms of the amplification process.
64 citations
TL;DR: The results link specific patterns of H3 acetylation to changes in nucleosome conformation that occur during transcription.
56 citations