Aziz, Shakila (1979) A study of RNA synthesis and its control in isolated macronuclei from Tetrahymena. PhD thesis, University of Warwick.

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Abstract

1. Using the initiation inhibitors rifamycin AF/013 and heparin, it has been shown that isolated macronuclei from Tetrahymena are not capable of reinitiating RNA synthesis in vitro in the absence of cytoplasm. However, they do appear to be able to elongate RNA chains that were initiated in vivo.

2. Macronuclei were found to be able to synthesize discrete species of RNA under standard assay conditions. These RNA species have been characterised so far only in terms of their sizes. The species of RNA which have been observed on gel electrophoresis are 25S, 17S, 15-8S and 4-5S, together with one or two additional minor species.

The 15-OS broad band, tentatively identified as mRNA, was only observed as a discrete peak in experiments in which nuclei were incubated in the presence of heparin. The other peaks have S values similar to ribosomal RNAs (25S, 17S and 5S) and transfer RNA (4S) as characterised in iri vivo experiments.

3. It has been shown that Tetrahymena contains separate pools of free and template engaged RNA polymerase I and II. The size of these pools depends on the physiological state of the cells (growth conditions). Macronuclei from starved cells had 17% of the transcriptional activity of those from exponential cells, but it was shown that the former nuclei had a greater ratio of free to engaged RNA polymerase than the latter.

4. RNA synthesis in isolated macronuclei from exponential cells was stimulated on addition of cytoplasmic extract from rapidly dividing Tetrahymena cells. The stimulation was not very great and amounted to only 35% above control. However, RNA synthesis in macronuclei isolated from starved Tetrahymena cells was stimulated 100% by cytoplasmic extract from exponential cells.

It was also shown that RNA synthesis in isolated macronuclei could be stimulated by the cytoplasmic extracts obtained from Xenopus oocytes and chick embryo. The extent of stimulation in this case was about 80%.

It was concluded that at least some of the factors stimulating nuclear transcription were not species specific.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QH Natural history Q Science > QL Zoology Q Science > QP Physiology
Library of Congress Subject Headings (LCSH):	Tetrahymena, RNA -- Synthesis, Cell nuclei -- Separation
Official Date:	November 1979
Dates:	Date Event November 1979 Submitted
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Swoboda, Bennett Edward Paul
Sponsors:	British Council
Extent:	131 leaves
Language:	eng

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