Nucleolar chromatin

About: Nucleolar chromatin is a research topic. Over the lifetime, 170 publications have been published within this topic receiving 6776 citations.

Ultrastructural organization of carcinoma Lewis (3LL) cells during cisplatin resistance formation

Abstract: The electron-microscopic analysis of the morphological status of 3LL (Lewis) carcinoma tumour cells in the process of cisplatin resistant phenotype formation has been performed. It was shown that selection of tumour cells forming cell clones characterized by more complicated nuclear and cytoplasm organization took place. The tumour cells had the diffused nuclear chromatin; nuclear envelope had the numerous pores with expanded diaphragms. The prominent nucleoli consisted of the active centres surrounded by considerable areas of the condensed nucleolar chromatin. Cell cytoplasm contained the well-developed Goldgi complex and the numerous well-structured myelinoid formations in the form of dense-wrapped concentric membrane structures. The obtained data can morphologically confirm the hypothesis of Gately D.P. and Howel S.B., 1993, thain the process of resistant phenotype formation the tumour cells can create the cellular mechanisms to remove the drug from the cell and to correct the damages of the cellular nucleus and cytoplasm.

Purificationand PartialCharacterizationof NucleolarAntigen-I of the NovikoffHepatoma'

Abstract: A nucleolarchromatinantigen(NoAg-1)found in Novikoff hepatoma but not in normal liver has been purified to homogeneityas shownby two-dimensionalgel electropho resis.initial purification of NoAg-1waspartiallyachievedby isolation of nucleolar chromatin and fractionation of its proteinsby successiveextractionwith solutionsof increas ing salt concentration. Further purification of this antigen was achievedby affinity and hydroxylapatitechromatogra phy. Although approximately50% of the NoAg-1antigen was in the 0.6 M NaCiextract of Novikoff nucleoli, it was less pure than in the 2 M NaCI:5 M urea extract which contained25%of the NoAg-1at a purity of 40%.The highly purified NoAg-1 had an approximate molecular weight of 60,000 and p1 of 5.1 ; the yield of NoAg-1 was 0.22% of the total nucleolarproteins.

A novel histone H4 variant regulates rDNA transcription in breast cancer

Abstract: Histone variants, present in various cell types and tissues, are known to exhibit different functions. For example, histone H3.3 and H2A.Z are both involved in gene expression regulation, whereas H2A.X is a specific variant that responds to DNA double-strand breaks. In this study, we characterized H4G, a novel hominidae-specific histone H4 variant. H4G expression was found in a variety of cell lines and was particularly overexpressed in the tissues of breast cancer patients. H4G was found to localize primarily to the nucleoli of the cell nucleus. This localization was controlled by the interaction of the alpha helix 3 of the histone fold motif with the histone chaperone, nucleophosphomin 1. In addition, we found that H4G nucleolar localization increased rRNA levels, protein synthesis rates, and cell cycle progression. Furthermore, micrococcal nuclease digestion of H4G-containing nucleosomes reconstituted in vitro indicated that H4G destabilizes the nucleosome, which may serve to alter nucleolar chromatin in a way that enhances rDNA transcription in breast cancer tissues.

The Structure and Function of Chromatin in Lower Eukaryotes

Abstract: One of the most important and exciting unsolved problems in molecular biology is concerned with the differential expression of the genetic information in eukaryotic organisms. Although the issue is by no means clearly resolved it is generally assumed that the heart of this problem lies at the level of transcriptional control rather than at the later stages of translation or post-translation, and it is at the genetic material itself, the chromatin, that attention has been primarily focused for clues to the nature of the control process. Transcription of m-RNA occurs in three stages: initiation which is the binding of RNA polymerase to a specific recognition site in the DNA; elongation which is the sequential production of m-RNA on one stand of the DNA template; termination, which is the release of the completed m-RNA and also, presumably, the RNA polymerase. Control of the rate of transcription may operate at any or all of these stages.

DNA localization in the nucleoli of sea urchin Paracentrotus lividus oocytes.

Abstract: It is known that in oocytes of P. lividus the nucleus contains a single giant nucleolus of unusual structure where intensive rRNA synthesis occurs. However, the questions of structural and functional relationships between the nucleolar compartments and the sites of active rRNA transcription still remain open. In the present work, we studied the chromatin organization in the nucleoli of P. lividus oocytes using Feulgen's and osmium amine staining procedures. Our results indicate that nucleolar chromatin of small (immature) oocytes differs from that in large mature oocytes. At the early stage of development, the DNA filamentous network 0.2-0.5 microm in diameter is formed in the nucleoli. Profound changes in the structure of the nucleolar DNA are observed in the course of oogenesis. Thus, at the late stage of development, the nucleolar chromatin forms characteristic ring-like structures, which indicates a non-uniform distribution of active ribosomal genes. A model of structural organization of the P. lividus nucleolus is discussed.