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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01 Dec 1978
TL;DR: Tandemly repeating units representing ribosomal transcriptional events, although few in number because of the procedure employed, clearly confirmed results of other techniques which revealed the unusually long length of the untranscribed spacer intercepts in mouse nucleolar chromatin.
Abstract: Electron microscopic studies of transcribed cellular deoxynucleoprotein (DNP) fibers from mouse kidney cells abortively infected with Simian Virus 40 (SV 40) revealed two types of transcriptional complexes. Tandemly repeating units representing ribosomal transcriptional events, although few in number because of the procedure employed, clearly confirmed results of other techniques which revealed the unusually long length of the untranscribed spacer intercepts in mouse nucleolar chromatin. In non-nucleolar arrays the density of the ribonucleoprotein (RNP) fibrils varied, as did the length and configuration of the associated DNP fibers. A statistical correlation between a "smooth" appearance of a transcribed portion of a DNP fiber and a high density of nascent RNP fibrils was observed.
6 citations
TL;DR: In okadaic acid treated HeLa cells, the chromosomes sometimes condense without being accompanied by nuclear envelope breakdown, which strongly speak for the localization of nucleolar chromatin (ribosomal cistrons) within the dense nucleolar component of the interphase nucleolus.
6 citations
Journal Article•
TL;DR: Results indicate that the fidelity of nucleolar readouts is controlled by regulatory proteins of the nucleolar chromatin.
Abstract: To compare regulation of nucleolar function of tumors and other tissues, it was necessary to develop assays of the fidelity of ribosomal DNA readouts. For this purpose, homochromatography analyses of complete T1 ribonuclease digestion products of the in vivo labeled 45 S preribosomal RNA were compared with those of 18S and of 28 S ribosomal RNA. Homochromatography analysis of the in vitro readout product of isolated nucleoli showed the presence of many large marker nucleotides of the in vivo 45 S preribosomal RNA. Moreover, no other large oligonucleotides were detected. The in vitro readout product of nucleolar chromatin had the same T1 ribonuclease digestion products, including the large marker of oligonucleotides. However, the in vitro readout product of nucleolar DNA contained no large marker T1 ribonuclease oligonucleotides. These results indicate that the fidelity of nucleolar readouts is controlled by regulatory proteins of the nucleolar chromatin. Differences were found in nucleolar proteins of normal rat liver and Novikoff hepatoma by immunological analyses. The possibility exists that differences in readout rates of tumor and other nucleoli are related to the protein difference detected by these immunological studies.
5 citations
TL;DR: The ultrastructural observations have allowed us to consider each nucleolar fibrillar centre as an active zone in the nucleolar chromatin loop, and to propose a possible model for the organization of the different components of the nucleolus within it.
Abstract: This paper deals with the fine structure of the fibrillar centres of the nucleolus inAllium cepa cells in ultrathin, sections of in vivo fixed roots. The ultrastructural observations have allowed us to consider each nucleolar fibrillar centre as an active zone in the nucleolar chromatin loop, and to propose a possible model for the organization of the different components of the nucleolus within it.
5 citations
TL;DR: This chapter describes methods for nucleolar protein extraction and specific methods for assay and isolation of nucleolar enzymes, and outlines the methods for studies on nucleolar antigens.
Abstract: Publisher Summary This chapter describes methods for nucleolar protein extraction and specific methods for assay and isolation of nucleolar enzymes. The nucleolus contains a variety of proteins or protein subunits. The techniques to study the chromatin components of the nucleus that are also applicable to the nucleolar fraction of chromatin are discussed. The procedures that may be applied directly to isolated nucleoli prior to fractionation of nucleolar subcomponents include (1) sodium chloride-hydrochloric acid extraction of proteins, (2) chloroethanol extraction, (3) urea extraction procedure, (4) acid extraction, and (5) sodium dodecyl sulfate (SDS) extraction. For functional studies, it is advantageous to fractionate the nucleolus into “native” subcomponents prior to protein isolation. Several procedures are available for isolation of substructures such as nucleolar chromatin, preribosomal ribonucleoprotein (RNP) particles, and fibrillar elements. There are numerous enzymes involved in the assembly and processing of preribosomal particles for which no functional assay is available. The chapter also outlines the methods for studies on nucleolar antigens.
5 citations