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Nucleolar localization of human methionyl-tRNA …

T1 - Nucleolar localization of human methionyl-tRNA synthetase and its role in ribosomal RNA synthesis

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rRNA synthesis in the nucleolus - ResearchGate

The relationship of ribosomal RNA (rRNA) synthesis to nucleolar ultrastructure was studied in partial nucleolar mutants of Xenopus laevis. These mutations are the result of a partial deletion of rRNA genes and therefore alow studies on nucleolar structure and function without using drugs that inhibit rRNA synthesis. Ultrastructural studies demonstrated that normal embryos have reticulated nucleoli that are composed of a loose meshwork of granules and fibrils and a typical nucleolonema. In contrast, partial nucleolar mutants in which rRNA synthesis is reduced to less than 50% of the normal rate have compact nucleoli and nucleolus-like bodies. The compace nucleoli contain granules and fibrils, but they are segregated into distinct regions, and a nucleolonema is never seen. Since other species of RNA are synthesized normally by partial nucleolar mutants, these results demonstrate that nucleolar segragation is related specifically to a reduction in rRNA synthesis. The nucleolus-like bodies are composed mainly of fibrils,and the number of such bodies are composed mainly of fibrils, and the number of such bodies present in the different nucleolar mutants is inversely related to the relative rate of rRNA synthesis. Although the partial nucleolar organizers produce segregated nucleoli in these mutants, they organize morphologically normal, but smaller, nucleoli in heterozygous embryos. Alternative explanations to account for these results are discussed.

Wolin SL and Matera AG (1999) The trials and travels of tRNA. Genes & Development 13: 1–10.

Lewis MS , Pikaard DJ , Nasrallah M , Doelling JH and Pikaard CS (2007) Locus‐specific ribosomal RNA gene silencing in nucleolar dominance. PLoS One 2: e815.

The relationship of ribosomal RNA synthesis ..

Raué HA (2004) Pre‐ribosomal RNA processing and assembly in Saccharomyces cerevisiae. In: Olson MOJ, (ed). The Nucleolus, pp. 199–222. Austin, TX: Landes Bioscience.

Lin T, Meng L, Lin T‐C, et al. (2014) Nucleostemin and GNL3L exercise distinct functions in genome protection and ribosome synthesis. Journal of Cell Science 127: 2302–2312.

How ribosomes are synthesized in the nucleolus? ~ …

AB - The nucleolus is the site of ribosome synthesis in the nucleus, whose integrity is essential. Epigenetic mechanisms are thought to regulate the activity of the ribosomal RNA (rRNA) gene copies, which are part of the nucleolus. Here we show that human cells lacking DNA methyltransferase 1 (Dnmt1), but not Dnmt33b, have a loss of DNA methylation and an increase in the acetylation level of lysine 16 histone H4 at the rRNA genes. Interestingly, we observed that SirT1, a NAD+-dependent histone deacetylase with a preference for lysine 16 H4, interacts with Dnmt1; and SirT1 recruitment to the rRNA genes is abrogated in Dnmt1 knockout cells. The DNA methylation and chromatin changes at ribosomal DNA observed are associated with a structurally disorganized nucleolus, which is fragmented into small nuclear masses. Prominent nucleolar proteins, such as Fibrillarin and Ki-67, and the rRNA genes are scattered throughout the nucleus in Dnmt1 deficient cells. These findings suggest a role for Dnmt1 as an epigenetic caretaker for the maintenance of nucleolar structure.

Sollner‐Webb B, Tycowski KT and Steitz JA (1996) Ribosomal RNA processing in eukaryotes. In: Zimmerman RA and Dahlberg AE, (eds). Ribosomal RNA: Structure Evolution, Gene Expression and Function in Protein Synthesis, pp. 469–490. Boca Raton, FL: CRC Press.

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  • of ribosome sub unit synthesis in the nucleolus ..

    KW - Methionyl-tRNA synthetase

  • Absence of ribosomal Rna synthesis in the ..

    KW - Ribosomal RNA synthesis

  • Ribosomal RNA synthesis plays a …

    After transcription of the pre-ribosomal RNAs, most steps in eukaryotic ribosome synthesis occur within the nucleolus

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CiteSeerX — THE RELATIONSHIP OF RIBOSOMAL RNA SYNTHESIS …

Durica DS and Krider HM (1978) Studies on the ribosomal RNA cistrons in Drosophila hybrids. II. Heterochromatic regions mediating nucleolar dominance. Genetics 89: 37–64.

The ribosome is a highly complex cellular machine

The nucleus is surrounded by the nuclear membrane
ribosome - small organelles composed of RNA-rich cytoplasmic granules that are sites of protein synthesis.
rough endoplasmic reticulum - (rough ER) a vast system of interconnected, membranous, infolded and convoluted sacks that are located in the cell's cytoplasm (the ER is continuous with the outer nuclear membrane).

This tutorial introduces the cell nucleus

Chen ZJ , Comai L and Pikaard CS (1998) Gene dosage and stochastic effects determine the severity and direction of uniparental ribosomal RNA gene silencing (nucleolar dominance) in Arabidopsis allopolyploids. Proceedings of the National Academy of Sciences of the USA 95: 14891–14896.

Nucleolus: Structure and Function

N2 - The nucleolus is the site of ribosome synthesis in the nucleus, whose integrity is essential. Epigenetic mechanisms are thought to regulate the activity of the ribosomal RNA (rRNA) gene copies, which are part of the nucleolus. Here we show that human cells lacking DNA methyltransferase 1 (Dnmt1), but not Dnmt33b, have a loss of DNA methylation and an increase in the acetylation level of lysine 16 histone H4 at the rRNA genes. Interestingly, we observed that SirT1, a NAD+-dependent histone deacetylase with a preference for lysine 16 H4, interacts with Dnmt1; and SirT1 recruitment to the rRNA genes is abrogated in Dnmt1 knockout cells. The DNA methylation and chromatin changes at ribosomal DNA observed are associated with a structurally disorganized nucleolus, which is fragmented into small nuclear masses. Prominent nucleolar proteins, such as Fibrillarin and Ki-67, and the rRNA genes are scattered throughout the nucleus in Dnmt1 deficient cells. These findings suggest a role for Dnmt1 as an epigenetic caretaker for the maintenance of nucleolar structure.

19/01/2018 · The cell is the basic unit of life

Caudy AA and Pikaard CS (2002) Xenopus ribosomal RNA gene intergenic spacer elements conferring transcriptional enhancement and nucleolar dominance‐like competition in oocytes. Journal of Biological Chemistry 277: 31577–31584.

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