The Relationship of the Nucleolus to the Synthesis of Ribosomal Rna in Hela Cells

McConkey, Edwin H.; Hopkins, J. W.

doi:10.1073/pnas.51.6.1197

Cited by 147 publications

(31 citation statements)

References 21 publications

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“…After the administration of a singIe dose of T3 of 30 pg/lOO g BW, the activity of the RNA polymerase I increased by 50% at 10 h and by 120% at 24 h. The effect on RNA polymerase I1 was less pronounced, with a 45% stimulation at 24 h. Thus, it seems that the effect of T3 on transcription mainly involves an increase in the synthesis of rRNA; the action of thyroid hormones would then be related with the formation of ribosomes. Since the ribosomal DNA cistrons are located in the nucleolus (McConkey & Hopkins, 1964), it may represent the subcellular site of thyroid hormone action. This is consistent with the recent observations of morphologic changes of the nucleolus after administration of T3 (Bailey et al, 1975), and the possible association of the hormone receptor with nucleolar chromatin (Gardner, 1975).…”

Section: Ejyects On Transcriptionmentioning

confidence: 99%

The Action of Thyroid Hormone

Bernal

Refetoff

1977

Clinical Endocrinology

104

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SUMMARYThyroid hormone affects both developmental and metabolic processes. It has a relatively specific effect on the synthesis of a number of enzymes and other proteins. The fundamental cellular mechanism of action seems to be at the level of genetic regulation. It involves interaction with nuclear receptors, leading to an activation of the protein synthesizing machinery. How binding to receptors is coupled to genetic activation is completely unknown. At least part of the metabolic effects of thyroid hormone could be mediated through an interaction with mitochondria and cell membrane, and with some enzymatic systems such as adenylcyclase.

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Section: Ejyects On Transcriptionmentioning

confidence: 99%

The Action of Thyroid Hormone

Bernal

Refetoff

1977

Clinical Endocrinology

104

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“…These genes are composed of repeated sequences that are present about 100 times per nucleus. The individual members of this group of DNA sequences are essentially identical.The amount of DNA that codes for ribosomal RNA is different in different organisms (1)(2)(3)(4)(5). The amount of Neurospora crassa DNA homologous to ribosomal RNA (rRNA) is almost 1% (4).…”

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confidence: 99%

Ribosomal RNA Genes of Neurospora: Isolation and Characterization

Chattopadhyay

Kohne²,

Dutta

1972

Proc. Natl. Acad. Sci. U.S.A.

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DNA sequences in Neurospora crassa that code for ribosomal RNA have been isolated in a highly purified state by DNA-RNA hybridization. About 100 separate ribosomal RNA genes exist in each nucleus. These genes are composed of repeated sequences that are present about 100 times per nucleus. The individual members of this group of DNA sequences are essentially identical.The amount of DNA that codes for ribosomal RNA is different in different organisms (1)(2)(3)(4)(5). The amount of Neurospora crassa DNA homologous to ribosomal RNA (rRNA) is almost 1% (4). Neurospora contains very little (unpublished data), if any, repeated DNA, besides multiple mitochondrial and ribosomal gene sequences. Thus, DNA sequences coding for rRNA are readily isolated by techniques used for the isolation of highly purified rRNA cistrons from bacteria (1). METHODSNeurospora crassa strain 74A was used in these studies. Conventional methods for isolation of DNA do not work well with Neurospora; Neurospora DNA was isolated by a modification of the urea-phosphate method (6). Lyophilized mycelial powder was suspended in a solution of 8 M urea, 0.24 M phosphate buffer (made of equimolar quantities of Na2HPO4 and NaH2PO4; molarity refers to the phosphate; pH 6.8), 1% sodiuni dodecyl sulfate, and 0.1 mM ethylenediamine tetraacetic acid (EDTA). The mixture was homogenized in a closed container (filled with liquid to suppress foaming) with a Waring blendor for 2 min to reduce the size of DNA pieces.The solution was passed through a hydroxyapatite (Bio-Gel HTP, BioRad Labs, Richmond, Calif.) column equilibrated with 0.24 M phosphate buffer-8 M urea at room temperature (230); the column was washed with the same solution until the A260 of the effluent was zero. It was then washed with 14 mM phosphate buffer (pH 6.8) for removal of urea from the column.DNA was removed from the column by elution with 0.4 M phosphate buffer and concentrated by centrifugation overnight at 100,000 X g. The pellet was suspended in a small volume of 1 mM EDTA. The resulting DNA was very pure and ready to use. 90% or more of the diphenylamine-reacting material was recovered from the Neurospora powder by this method.[32P]DNAs (4) were checked for alkaline lability and acid solubility.[82P]DNAs used in these experiments routinely had less than 1% acid-soluble radioactivity, virtually no alkali-labile radioactivity (<0.1%o), and 95% or better DNase lability. All DNAs were sheared before use by passing them through an orifice with a pressure drop of 50,000 lb/in.2. The resulting pieces were about 300-500 nucleotides in length.t Present address: Biology Department, University of California, San Diego, La Jolla, Calif., 92037. 3256As a final purification step, a dilute solution of sheared Neurospora [82P]DNA (20-100 ,g/ml) was heat-denatured in 0.14 M phosphate buffer-0.4% sodium dodecyl sulfate and passed immediately through hydroxyapatite equilibrated to 0.14 M phosphate buffer-0.4% sodium dodecyl sulfate at 600. Single-stranded DNA passes through the column under these con...

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“…This fact is of interest in the light of present theories on nucleolar function. The increasing evidence that nucleoli are involved in ribosomal RNA (rRNA) synthesis has been summarised by, amongst others, McConkey and Hopkins (1964) and Perry (1967). This evidence would suggest that the rRNA and possibly protein (Perry, 1967) of the ribosomes in hybrids showing marked nucleolar suppression is formed very largely in the nucleolus of the nonsuppressed parent.…”

Section: Discussionmentioning

confidence: 99%

Nucleolar suppression, its inheritance and association with taxonomy and sex in the genus Ribes

Keep¹

1971

Heredity

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The Relationship of the Nucleolus to the Synthesis of Ribosomal Rna in Hela Cells

Cited by 147 publications

References 21 publications

The Action of Thyroid Hormone

The Action of Thyroid Hormone

Ribosomal RNA Genes of Neurospora: Isolation and Characterization

Nucleolar suppression, its inheritance and association with taxonomy and sex in the genus Ribes

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