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The ribosomal genes and nucleoli of Dictyostelium discoideum : studies on the regulation of gene expression

The ribosomal genes and nucleoli of Dictyostelium discoideum : studies on the regulation of gene expression
The ribosomal genes and nucleoli of Dictyostelium discoideum : studies on the regulation of gene expression

The cellular slime-mould Dictyostelium discoideum shows an unusual organisation of its ribosomal RNA (rRNA) genes. These are found on gi-

ant, extrachromosomal, palindromic dimers, present throughout the asexual life-cycle (a pattern of organisation found in only a few lower eukaryotcs). Furthermore, a distinct pattern of developmentally regulated gene expression is observed, with a large drop in rDNA transcriptional activity at the onset of development. The aim of the work presented in this thesis was to investigate some possible mechanisms involved in the regulated expression of these genes, at a primary level, that of transcription.

Control of the rRNA genes at a gross level was studied by electron microscopy, studying the ultrastructure of the nucleolus (the nuclear location of these genes) both during the asexual cell cycle and with development.

On a molecular level, the state of methylation of the rRNA genes was investigated. Evidence was sought for an involvement of DNA methylation in the regulation of gene expression (as is seen in higher eukaryotes) and/or for a restriction/modification mechanism, based on base methylation, that might be implicated in the control of rDNA molecules through amplification (as has been demonstrated for the rRNA genes of Tetrahymena that show a very similar pattern of organisation). No evidence was found for either mechanism in Dictyostelium.

Preliminary experimental results are also presented from studies on the chromatin structure of the rRNA genes and on the control of their replication during the cell cycle.

University of Southampton
Bradley, Mairead Christina
Bradley, Mairead Christina

Bradley, Mairead Christina (1988) The ribosomal genes and nucleoli of Dictyostelium discoideum : studies on the regulation of gene expression. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The cellular slime-mould Dictyostelium discoideum shows an unusual organisation of its ribosomal RNA (rRNA) genes. These are found on gi-

ant, extrachromosomal, palindromic dimers, present throughout the asexual life-cycle (a pattern of organisation found in only a few lower eukaryotcs). Furthermore, a distinct pattern of developmentally regulated gene expression is observed, with a large drop in rDNA transcriptional activity at the onset of development. The aim of the work presented in this thesis was to investigate some possible mechanisms involved in the regulated expression of these genes, at a primary level, that of transcription.

Control of the rRNA genes at a gross level was studied by electron microscopy, studying the ultrastructure of the nucleolus (the nuclear location of these genes) both during the asexual cell cycle and with development.

On a molecular level, the state of methylation of the rRNA genes was investigated. Evidence was sought for an involvement of DNA methylation in the regulation of gene expression (as is seen in higher eukaryotes) and/or for a restriction/modification mechanism, based on base methylation, that might be implicated in the control of rDNA molecules through amplification (as has been demonstrated for the rRNA genes of Tetrahymena that show a very similar pattern of organisation). No evidence was found for either mechanism in Dictyostelium.

Preliminary experimental results are also presented from studies on the chromatin structure of the rRNA genes and on the control of their replication during the cell cycle.

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Published date: 1988

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Local EPrints ID: 460785
URI: http://eprints.soton.ac.uk/id/eprint/460785
PURE UUID: 80119d3f-b64f-46d6-b852-085479ed3da7

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Date deposited: 04 Jul 2022 18:29
Last modified: 04 Jul 2022 18:29

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Author: Mairead Christina Bradley

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